[mysql] Should I use the datetime or timestamp data type in MySQL?

Would you recommend using a datetime or a timestamp field, and why (using MySQL)?

I'm working with PHP on the server side.

+---------------------------------------------------------------------------------------+--------------------------------------------------------------------------+
|                                       TIMESTAMP                                       |                                 DATETIME                                 |
+---------------------------------------------------------------------------------------+--------------------------------------------------------------------------+
| TIMESTAMP requires 4 bytes.                                                           | DATETIME requires 8 bytes.                                               |
| Timestamp is the number of seconds that have elapsed since January 1, 1970 00:00 UTC. | DATETIME is a text displays 'YYYY-MM-DD HH:MM:SS' format.                |
| TIMESTAMP supported range: ‘1970-01-01 00:00:01' UTC to ‘2038-01-19 03:14:07' UTC.    | DATETIME supported range: ‘1000-01-01 00:00:00' to ‘9999-12-31 23:59:59' |
| TIMESTAMP during retrieval converted back to the current time zone.                   | DATETIME can not do this.                                                |
| TIMESTAMP is used mostly for metadata i.e. row created/modified and audit purpose.    | DATETIME is used mostly for user-data.                                   |
+---------------------------------------------------------------------------------------+--------------------------------------------------------------------------+

I like a Unix timestamp, because you can convert to numbers and just worry about the number. Plus you add/subtract and get durations, etc. Then convert the result to Date in whatever format. This code finds out how much time in minutes passed between a timestamp from a document, and the current time.

$date  = $item['pubdate']; (etc ...)
$unix_now = time();
$result = strtotime($date, $unix_now);
$unix_diff_min = (($unix_now  - $result) / 60);
$min = round($unix_diff_min);

TIMESTAMP is 4 bytes Vs 8 bytes for DATETIME.

http://dev.mysql.com/doc/refman/5.0/en/storage-requirements.html

But like scronide said it does have a lower limit of the year 1970. It's great for anything that might happen in the future though ;)

I make this decision on a semantic base.

I use a timestamp when I need to record a (more or less) fixed point in time. For example when a record was inserted into the database or when some user action took place.

I use a datetime field when the date/time can be set and changed arbitrarily. For example when a user can save later change appointments.

I like a Unix timestamp, because you can convert to numbers and just worry about the number. Plus you add/subtract and get durations, etc. Then convert the result to Date in whatever format. This code finds out how much time in minutes passed between a timestamp from a document, and the current time.

$date  = $item['pubdate']; (etc ...)
$unix_now = time();
$result = strtotime($date, $unix_now);
$unix_diff_min = (($unix_now  - $result) / 60);
$min = round($unix_diff_min);

TIMESTAMP is 4 bytes Vs 8 bytes for DATETIME.

http://dev.mysql.com/doc/refman/5.0/en/storage-requirements.html

But like scronide said it does have a lower limit of the year 1970. It's great for anything that might happen in the future though ;)

TIMESTAMP is always in UTC (that is, elapsed seconds since 1970-01-01, in UTC), and your MySQL server auto-converts it to the date/time for the connection timezone. In the long-term, TIMESTAMP is the way to go because you know your temporal data will always be in UTC. For example, you won't screw your dates up if you migrate to a different server or if you change the timezone settings on your server.

Note: default connection timezone is the server timezone, but this can (should) be changed per session (see SET time_zone = ...).

A lot of answers here suggest to store as timestamp in the case you have to represent well defined points in time. But you can also have points in time with datetime if you store them all in UTC by convention.

TIMESTAMP is always in UTC (that is, elapsed seconds since 1970-01-01, in UTC), and your MySQL server auto-converts it to the date/time for the connection timezone. In the long-term, TIMESTAMP is the way to go because you know your temporal data will always be in UTC. For example, you won't screw your dates up if you migrate to a different server or if you change the timezone settings on your server.

Note: default connection timezone is the server timezone, but this can (should) be changed per session (see SET time_zone = ...).

It is worth noting in MySQL you can use something along the lines of the below when creating your table columns:

on update CURRENT_TIMESTAMP

This will update the time at each instance you modify a row and is sometimes very helpful for stored last edit information. This only works with timestamp, not datetime however.

Beware of timestamp changing when you do a UPDATE statement on a table. If you have a table with columns 'Name' (varchar), 'Age' (int), and 'Date_Added' (timestamp) and you run the following DML statement

UPDATE table
SET age = 30

then every single value in your 'Date_Added' column would be changed to the current timestamp.

The major difference is

• a INDEX's on Timestamp - works
• a INDEX's on Datetime - Does not work

look at this post to see problems with Datetime indexing

I make this decision on a semantic base.

I use a timestamp when I need to record a (more or less) fixed point in time. For example when a record was inserted into the database or when some user action took place.

I use a datetime field when the date/time can be set and changed arbitrarily. For example when a user can save later change appointments.

I recommend using neither a DATETIME or a TIMESTAMP field. If you want to represent a specific day as a whole (like a birthday), then use a DATE type, but if you're being more specific than that, you're probably interested in recording an actual moment as opposed to a unit of time (day,week,month,year). Instead of using a DATETIME or TIMESTAMP, use a BIGINT, and simply store the number of milliseconds since the epoch (System.currentTimeMillis() if you're using Java). This has several advantages:

1. You avoid vendor lock-in. Pretty much every database supports integers in the relatively similar fashion. Suppose you want to move to another database. Do you want to worry about the differences between MySQL's DATETIME values and how Oracle defines them? Even among different versions of MySQL, TIMESTAMPS have a different level of precision. It was only just recently that MySQL supported milliseconds in the timestamps.
2. No timezone issues. There's been some insightful comments on here on what happens with timezones with the different data types. But is this common knowledge, and will your co-workers all take the time to learn it? On the other hand, it's pretty hard to mess up changing a BigINT into a java.util.Date. Using a BIGINT causes a lot of issues with timezones to fall by the wayside.
3. No worries about ranges or precision. You don't have to worry about what being cut short by future date ranges (TIMESTAMP only goes to 2038).
4. Third-party tool integration. By using an integer, it's trivial for 3rd party tools (e.g. EclipseLink) to interface with the database. Not every third-party tool is going to have the same understanding of a "datetime" as MySQL does. Want to try and figure out in Hibernate whether you should use a java.sql.TimeStamp or java.util.Date object if you're using these custom data types? Using your base data types make's use with 3rd-party tools trivial.

This issue is closely related how you should store a money value (i.e. $1.99) in a database. Should you use a Decimal, or the database's Money type, or worst of all a Double? All 3 of these options are terrible, for many of the same reasons listed above. The solution is to store the value of money in cents using BIGINT, and then convert cents to dollars when you display the value to the user. The database's job is to store data, and NOT to intrepret that data. All these fancy data-types you see in databases(especially Oracle) add little, and start you down the road to vendor lock-in.

TIMESTAMP is 4 bytes Vs 8 bytes for DATETIME.

http://dev.mysql.com/doc/refman/5.0/en/storage-requirements.html

But like scronide said it does have a lower limit of the year 1970. It's great for anything that might happen in the future though ;)

The below examples show how the TIMESTAMP date type changed the values after changing the time-zone to 'america/new_york' where DATETIMEis unchanged.

mysql> show variables like '%time_zone%';
+------------------+---------------------+
| Variable_name    | Value               |
+------------------+---------------------+
| system_time_zone | India Standard Time |
| time_zone        | Asia/Calcutta       |
+------------------+---------------------+

mysql> create table datedemo(
    -> mydatetime datetime,
    -> mytimestamp timestamp
    -> );

mysql> insert into datedemo values ((now()),(now()));

mysql> select * from datedemo;
+---------------------+---------------------+
| mydatetime          | mytimestamp         |
+---------------------+---------------------+
| 2011-08-21 14:11:09 | 2011-08-21 14:11:09 |
+---------------------+---------------------+

mysql> set time_zone="america/new_york";

mysql> select * from datedemo;
+---------------------+---------------------+
| mydatetime          | mytimestamp         |
+---------------------+---------------------+
| 2011-08-21 14:11:09 | 2011-08-21 04:41:09 |
+---------------------+---------------------+

I've converted my answer into article so more people can find this useful, MySQL: Datetime Versus Timestamp Data Types.

I always use a Unix timestamp, simply to maintain sanity when dealing with a lot of datetime information, especially when performing adjustments for timezones, adding/subtracting dates, and the like. When comparing timestamps, this excludes the complicating factors of timezone and allows you to spare resources in your server side processing (Whether it be application code or database queries) in that you make use of light weight arithmetic rather then heavier date-time add/subtract functions.

Another thing worth considering:

If you're building an application, you never know how your data might have to be used down the line. If you wind up having to, say, compare a bunch of records in your data set, with, say, a bunch of items from a third-party API, and say, put them in chronological order, you'll be happy to have Unix timestamps for your rows. Even if you decide to use MySQL timestamps, store a Unix timestamp as insurance.

1. TIMESTAMP is four bytes vs eight bytes for DATETIME.

2. Timestamps are also lighter on the database and indexed faster.

3. The DATETIME type is used when you need values that contain both date and time information. MySQL retrieves and displays DATETIME values in ‘YYYY-MM-DD HH:MM:SS’ format. The supported range is ’1000-01-01 00:00:00' to ’9999-12-31 23:59:59'.

The TIMESTAMP data type has a range of ’1970-01-01 00:00:01' UTC to ’2038-01-09 03:14:07' UTC. It has varying properties, depending on the MySQL version and the SQL mode the server is running in.

4. DATETIME is constant while TIMESTAMP is effected by the time_zone setting.

A TIMESTAMP requires 4 bytes, whereas a DATETIME requires 8 bytes.

From my experiences, if you want a date field in which insertion happens only once and you don't want to have any update or any other action on that particular field, go with date time.

For example, consider a user table with a REGISTRATION DATE field. In that user table, if you want to know the last logged in time of a particular user, go with a field of timestamp type so that the field gets updated.

If you are creating the table from phpMyAdmin the default setting will update the timestamp field when a row update happens. If your timestamp filed is not updating with row update, you can use the following query to make a timestamp field get auto updated.

ALTER TABLE your_table
      MODIFY COLUMN ts_activity TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;

timestamp is a current time of an event recorded by a computer through Network Time Protocol (NTP).

datetime is a current timezone that is set in your PHP configuration.

The main difference is that DATETIME is constant while TIMESTAMP is affected by the time_zone setting.

So it only matters when you have — or may in the future have — synchronized clusters across time zones.

In simpler words: If I have a database in Australia, and take a dump of that database to synchronize/populate a database in America, then the TIMESTAMP would update to reflect the real time of the event in the new time zone, while DATETIME would still reflect the time of the event in the au time zone.

A great example of DATETIME being used where TIMESTAMP should have been used is in Facebook, where their servers are never quite sure what time stuff happened across time zones. Once I was having a conversation in which the time said I was replying to messages before the message was actually sent. (This, of course, could also have been caused by bad time zone translation in the messaging software if the times were being posted rather than synchronized.)

1. TIMESTAMP is four bytes vs eight bytes for DATETIME.

2. Timestamps are also lighter on the database and indexed faster.

3. The DATETIME type is used when you need values that contain both date and time information. MySQL retrieves and displays DATETIME values in ‘YYYY-MM-DD HH:MM:SS’ format. The supported range is ’1000-01-01 00:00:00' to ’9999-12-31 23:59:59'.

The TIMESTAMP data type has a range of ’1970-01-01 00:00:01' UTC to ’2038-01-09 03:14:07' UTC. It has varying properties, depending on the MySQL version and the SQL mode the server is running in.

4. DATETIME is constant while TIMESTAMP is effected by the time_zone setting.

I would always use a Unix timestamp when working with MySQL and PHP. The main reason for this being the default date method in PHP uses a timestamp as the parameter, so there would be no parsing needed.

To get the current Unix timestamp in PHP, just do time();
and in MySQL do SELECT UNIX_TIMESTAMP();.

I recommend using neither a DATETIME or a TIMESTAMP field. If you want to represent a specific day as a whole (like a birthday), then use a DATE type, but if you're being more specific than that, you're probably interested in recording an actual moment as opposed to a unit of time (day,week,month,year). Instead of using a DATETIME or TIMESTAMP, use a BIGINT, and simply store the number of milliseconds since the epoch (System.currentTimeMillis() if you're using Java). This has several advantages:

1. You avoid vendor lock-in. Pretty much every database supports integers in the relatively similar fashion. Suppose you want to move to another database. Do you want to worry about the differences between MySQL's DATETIME values and how Oracle defines them? Even among different versions of MySQL, TIMESTAMPS have a different level of precision. It was only just recently that MySQL supported milliseconds in the timestamps.
2. No timezone issues. There's been some insightful comments on here on what happens with timezones with the different data types. But is this common knowledge, and will your co-workers all take the time to learn it? On the other hand, it's pretty hard to mess up changing a BigINT into a java.util.Date. Using a BIGINT causes a lot of issues with timezones to fall by the wayside.
3. No worries about ranges or precision. You don't have to worry about what being cut short by future date ranges (TIMESTAMP only goes to 2038).
4. Third-party tool integration. By using an integer, it's trivial for 3rd party tools (e.g. EclipseLink) to interface with the database. Not every third-party tool is going to have the same understanding of a "datetime" as MySQL does. Want to try and figure out in Hibernate whether you should use a java.sql.TimeStamp or java.util.Date object if you're using these custom data types? Using your base data types make's use with 3rd-party tools trivial.

This issue is closely related how you should store a money value (i.e. $1.99) in a database. Should you use a Decimal, or the database's Money type, or worst of all a Double? All 3 of these options are terrible, for many of the same reasons listed above. The solution is to store the value of money in cents using BIGINT, and then convert cents to dollars when you display the value to the user. The database's job is to store data, and NOT to intrepret that data. All these fancy data-types you see in databases(especially Oracle) add little, and start you down the road to vendor lock-in.

In my case, I set UTC as a time zone for everything: the system, the database server, etc. every time that I can. If my customer requires another time zone, then I configure it on the app.

I almost always prefer timestamps rather than datetime fields, because timestamps include the timezone implicitly. So, since the moment that the app will be accessed from users from different time zones and you want them to see dates and times in their local timezone, this field type makes it pretty easy to do it than if the data were saved in datetime fields.

As a plus, in the case of a migration of the database to a system with another timezone, I would feel more confident using timestamps. Not to say possible issues when calculating differences between two moments with a sumer time change in between and needing a precision of 1 hour or less.

So, to summarize, I value this advantages of timestamp:

• ready to use on international (multi time zone) apps
• easy migrations between time zones
• pretty easy to calculate diferences (just subtract both timestamps)
• no worry about dates in/out a summer time period

For all this reasons, I choose UTC & timestamp fields where posible. And I avoid headaches ;)

A lot of answers here suggest to store as timestamp in the case you have to represent well defined points in time. But you can also have points in time with datetime if you store them all in UTC by convention.

Comparison between DATETIME, TIMESTAMP and DATE

What is that [.fraction]?

• A DATETIME or TIMESTAMP value can include a trailing fractional seconds part in up to microseconds (6 digits) precision. In particular, any fractional part in a value inserted into a DATETIME or TIMESTAMP column is stored rather than discarded. This is of course optional.

Sources:

• MySQL Date/Time data types reference
• MySQL Storage Requirements reference

I always use a Unix timestamp, simply to maintain sanity when dealing with a lot of datetime information, especially when performing adjustments for timezones, adding/subtracting dates, and the like. When comparing timestamps, this excludes the complicating factors of timezone and allows you to spare resources in your server side processing (Whether it be application code or database queries) in that you make use of light weight arithmetic rather then heavier date-time add/subtract functions.

Another thing worth considering:

If you're building an application, you never know how your data might have to be used down the line. If you wind up having to, say, compare a bunch of records in your data set, with, say, a bunch of items from a third-party API, and say, put them in chronological order, you'll be happy to have Unix timestamps for your rows. Even if you decide to use MySQL timestamps, store a Unix timestamp as insurance.

If you want to GUARANTEE your application will NOT function in February, 2038, use TIMESTAMP. Refer to your REFMAN for the RANGE of dates supported.

Beware of timestamp changing when you do a UPDATE statement on a table. If you have a table with columns 'Name' (varchar), 'Age' (int), and 'Date_Added' (timestamp) and you run the following DML statement

UPDATE table
SET age = 30

then every single value in your 'Date_Added' column would be changed to the current timestamp.

The timestamp data type stores date and time, but in UTC format, not in the current timezone format as datetime does. And when you fetch data, timestamp again converts that into the current timezone time.

So suppose you are in USA and getting data from a server which has a time zone of USA. Then you will get the date and time according to the USA time zone. The timestamp data type column always get updated automatically when its row gets updated. So it can be useful to track when a particular row was updated last time.

For more details you can read the blog post Timestamp Vs Datetime .

+---------------------------------------------------------------------------------------+--------------------------------------------------------------------------+
|                                       TIMESTAMP                                       |                                 DATETIME                                 |
+---------------------------------------------------------------------------------------+--------------------------------------------------------------------------+
| TIMESTAMP requires 4 bytes.                                                           | DATETIME requires 8 bytes.                                               |
| Timestamp is the number of seconds that have elapsed since January 1, 1970 00:00 UTC. | DATETIME is a text displays 'YYYY-MM-DD HH:MM:SS' format.                |
| TIMESTAMP supported range: ‘1970-01-01 00:00:01' UTC to ‘2038-01-19 03:14:07' UTC.    | DATETIME supported range: ‘1000-01-01 00:00:00' to ‘9999-12-31 23:59:59' |
| TIMESTAMP during retrieval converted back to the current time zone.                   | DATETIME can not do this.                                                |
| TIMESTAMP is used mostly for metadata i.e. row created/modified and audit purpose.    | DATETIME is used mostly for user-data.                                   |
+---------------------------------------------------------------------------------------+--------------------------------------------------------------------------+

A timestamp field is a special case of the datetime field. You can create timestamp columns to have special properties; it can be set to update itself on either create and/or update.

In "bigger" database terms, timestamp has a couple of special-case triggers on it.

What the right one is depends entirely on what you want to do.

In MySQL 5 and above, TIMESTAMP values are converted from the current time zone to UTC for storage, and converted back from UTC to the current time zone for retrieval. (This occurs only for the TIMESTAMP data type, and not for other types such as DATETIME.)

By default, the current time zone for each connection is the server's time. The time zone can be set on a per-connection basis, as described in MySQL Server Time Zone Support.

I always use DATETIME fields for anything other than row metadata (date created or modified).

As mentioned in the MySQL documentation:

The DATETIME type is used when you need values that contain both date and time information. MySQL retrieves and displays DATETIME values in 'YYYY-MM-DD HH:MM:SS' format. The supported range is '1000-01-01 00:00:00' to '9999-12-31 23:59:59'.

...

The TIMESTAMP data type has a range of '1970-01-01 00:00:01' UTC to '2038-01-09 03:14:07' UTC. It has varying properties, depending on the MySQL version and the SQL mode the server is running in.

You're quite likely to hit the lower limit on TIMESTAMPs in general use -- e.g. storing birthdate.

Not mentioned so far, is that DEFAULT CURRENT_TIMESTAMP only works with Timestamp, but not DateTime type fields.

This becomes relevant for MS Access tables which can only use DateTime but not Timestamp.

2016 +: what I advise is to set your Mysql timezone to UTC and use DATETIME:

Any recent front-end framework (Angular 1/2, react, Vue,...) can easily and automatically convert your UTC datetime to local time.

Additionally:

• DATETIME can now be automatically set to the current time value How do you set a default value for a MySQL Datetime column?
• Contrary to what one might think, DATETIME is FASTER THAN TIMESTAMP, http://gpshumano.blogs.dri.pt/2009/07/06/mysql-datetime-vs-timestamp-vs-int-performance-and-benchmarking-with-myisam/
• TIMESTAMP is still limited to 1970-2038

(Unless you are likely to change the timezone of your servers)

Example with AngularJs

// back-end: format for angular within the sql query
SELECT DATE_FORMAT(my_datetime, "%Y-%m-%dT%TZ")...

// font-end Output the localised time
{{item.my_datetime | date :'medium' }}

All localised time format available here: https://docs.angularjs.org/api/ng/filter/date

I merely use unsigned BIGINT while storing UTC ...

which then still can be adjusted to local time in PHP.

the DATETIME to be selected with FROM_UNIXTIME( integer_timestamp_column ).

one obviously should set an index on that column, else there would be no advance.

From my experiences, if you want a date field in which insertion happens only once and you don't want to have any update or any other action on that particular field, go with date time.

For example, consider a user table with a REGISTRATION DATE field. In that user table, if you want to know the last logged in time of a particular user, go with a field of timestamp type so that the field gets updated.

If you are creating the table from phpMyAdmin the default setting will update the timestamp field when a row update happens. If your timestamp filed is not updating with row update, you can use the following query to make a timestamp field get auto updated.

ALTER TABLE your_table
      MODIFY COLUMN ts_activity TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP;

A timestamp field is a special case of the datetime field. You can create timestamp columns to have special properties; it can be set to update itself on either create and/or update.

In "bigger" database terms, timestamp has a couple of special-case triggers on it.

What the right one is depends entirely on what you want to do.

Not mentioned so far, is that DEFAULT CURRENT_TIMESTAMP only works with Timestamp, but not DateTime type fields.

This becomes relevant for MS Access tables which can only use DateTime but not Timestamp.

The timestamp data type stores date and time, but in UTC format, not in the current timezone format as datetime does. And when you fetch data, timestamp again converts that into the current timezone time.

So suppose you are in USA and getting data from a server which has a time zone of USA. Then you will get the date and time according to the USA time zone. The timestamp data type column always get updated automatically when its row gets updated. So it can be useful to track when a particular row was updated last time.

For more details you can read the blog post Timestamp Vs Datetime .

TIMESTAMP is 4 bytes Vs 8 bytes for DATETIME.

http://dev.mysql.com/doc/refman/5.0/en/storage-requirements.html

But like scronide said it does have a lower limit of the year 1970. It's great for anything that might happen in the future though ;)

The below examples show how the TIMESTAMP date type changed the values after changing the time-zone to 'america/new_york' where DATETIMEis unchanged.

mysql> show variables like '%time_zone%';
+------------------+---------------------+
| Variable_name    | Value               |
+------------------+---------------------+
| system_time_zone | India Standard Time |
| time_zone        | Asia/Calcutta       |
+------------------+---------------------+

mysql> create table datedemo(
    -> mydatetime datetime,
    -> mytimestamp timestamp
    -> );

mysql> insert into datedemo values ((now()),(now()));

mysql> select * from datedemo;
+---------------------+---------------------+
| mydatetime          | mytimestamp         |
+---------------------+---------------------+
| 2011-08-21 14:11:09 | 2011-08-21 14:11:09 |
+---------------------+---------------------+

mysql> set time_zone="america/new_york";

mysql> select * from datedemo;
+---------------------+---------------------+
| mydatetime          | mytimestamp         |
+---------------------+---------------------+
| 2011-08-21 14:11:09 | 2011-08-21 04:41:09 |
+---------------------+---------------------+

I've converted my answer into article so more people can find this useful, MySQL: Datetime Versus Timestamp Data Types.

A DATETIME carries no timezone information with it and will always display the same independent of the timezone that is in effect for the session, which defaults to the server's timezone unless you have explicitly changed it. However, if I initialize a DATETIME column with a function such as NOW() rather than a literal such as '2020-01-16 12:15:00', then the value stored will, of course, be the current date and time localized to the session's timezone.

A TIMESTAMP by contrast does implicitly carry timezone information: When you initialize a TIMESTAMP column with a value, that value is converted to UTC before it is stored. If the value being stored is a literal such as '2020-01-16 12:15:00', it is interpreted as being in the session's current timezone for conversion purposes. Conversely, when a TIMESTAMP column is displayed, it will first be converted from UTC to the session's current timezone.

When to use one or the other? A Case Study

A Website for a community theater group is presenting several performances of a play for which it is selling tickets. The dates and times of these performances will appear in a drop down from which a customer wishing to buy tickets for a performance will select one. It would make sense for database column performance_date_and_time to be a DATETIME type. If the performance is in New York, there is an understanding that there is an implicit timezone involved ("New York local time") and ideally we would want the date and time to display as 'December 12, 2019 at 8:00 PM' regardless of the session's timezone and without having to go to the trouble of having to do any timezone conversions.

On the other hand, once the December 12th, 2019 8 PM performance began, we might no longer want to sell tickets for it and thus no longer display that performance in the drop down. So, we would like to be able to know whether '2019-12-12 20:00:00' has occurred or not. That would argue for having a TIMESTAMP column, setting the timezone for the session to 'America/New_York' with set session time_zone='America/New_York' and then storing '2019-12-12 20:00:00' into the TIMESTAMP column. Henceforth we can test for whether the performance has begun by comparing this column with NOW() independent of the current session timezone.

Or it might make sense to have a DATETIME and a TIMESTAMP column for these two separate purposes. Or not. Clearly, either one could serve both purposes. If you go with just a DATETIME column, then you must set the current timezone to your local timezone before comparing with NOW(). If you go with just a TIMESTAMP column, you must set the session timezone to your local timezone before displaying the column.

I prefer using timestamp so to keep everything in one common raw format and format the data in PHP code or in your SQL query. There are instances where it comes in handy in your code to keep everything in plain seconds.

timestamp is a current time of an event recorded by a computer through Network Time Protocol (NTP).

datetime is a current timezone that is set in your PHP configuration.

Comparison between DATETIME, TIMESTAMP and DATE

What is that [.fraction]?

• A DATETIME or TIMESTAMP value can include a trailing fractional seconds part in up to microseconds (6 digits) precision. In particular, any fractional part in a value inserted into a DATETIME or TIMESTAMP column is stored rather than discarded. This is of course optional.

Sources:

• MySQL Date/Time data types reference
• MySQL Storage Requirements reference

I make this decision on a semantic base.

I use a timestamp when I need to record a (more or less) fixed point in time. For example when a record was inserted into the database or when some user action took place.

I use a datetime field when the date/time can be set and changed arbitrarily. For example when a user can save later change appointments.

In MySQL 5 and above, TIMESTAMP values are converted from the current time zone to UTC for storage, and converted back from UTC to the current time zone for retrieval. (This occurs only for the TIMESTAMP data type, and not for other types such as DATETIME.)

By default, the current time zone for each connection is the server's time. The time zone can be set on a per-connection basis, as described in MySQL Server Time Zone Support.

I make this decision on a semantic base.

I use a timestamp when I need to record a (more or less) fixed point in time. For example when a record was inserted into the database or when some user action took place.

I use a datetime field when the date/time can be set and changed arbitrarily. For example when a user can save later change appointments.

Neither. The DATETIME and TIMESTAMP types are fundamentally broken for generic use cases. MySQL will change them in the future. You should use BIGINT and UNIX timestamps unless you have a specific reason to use something else.

Special cases

Here are some specific situations where your choice is easier and you don't need the analysis and general recommendation in this answer.

• Date only — if you only care about the date (like the date of the next Lunar New Year, 2020-02-25) AND you have a clear understanding of what timezone that date applies (or don't care, as in the case of Lunar New Year) then use the DATE column type.

• Record insert times — if you are logging the insert dates/times for rows in your database AND you don't care that your application will break in the next 19 years, then go ahead and use TIMESTAMP with a default value of CURRENT_TIMESTAMP().

Why is TIMESTAMP broken?

The TIMESTAMP type is stored on disk in UTC timezone. This means that if you physically move your server, it does not break. That's good ?. But timestamps as currently defined will stop working entirely in the year 2038 ?.

Every time you INSERT INTO or SELECT FROM a TIMESTAMP column, the physical location (i.e. timezone configuration) of your client/application server is taken into account. If you move your application server then your dates break ?.

Why is DATETIME broken?

A DATETIME stores a DATE and a TIME in the same column. Neither of these things have any meaning unless the timezone is understood, and the timezone is not stored anywhere ?. You should put the intended timezone as a comment in the column because the timezone is inextricably linked to the data. So few people use column comments, therefore this is mistake waiting to happen. I inherited a server from Arizona, so I always need to convert all timestamps FROM Arizona time and then TO another time.

The only situation a DATETIME is correct is to complete this sentence:

Your year 2020 solar new year starts at exactly DATETIME("2020-01-01 00:00:00").

There is no other good use for DATETIMEs. Perhaps you will imagine a web server for a city government in Delaware. Surely the timezone for this server and all the people accessing this server can be implied to be in Delaware, with Eastern Time Zone, right? Wrong! In this millennium, we all think of servers as existing in "the cloud". So it is always wrong to think of your server in any specific timezone, because your server will be moved some day.

Note: MySQL now supports time zone offsets in DATETIME literals (thanks @Marko). This may make inserting DATETIMEs more convenient for you but does not address the incomplete and therefore useless meaning of the data, this fatal issue identifie ("?") above.

How to use BIGINT?

Define:

CREATE TEMPORARY TABLE good_times (
    a_time BIGINT
)

Insert a specific value:

INSERT INTO good_times VALUES (
    UNIX_TIMESTAMP(CONVERT_TZ("2014-12-03 12:24:54", '+00:00', @@global.time_zone))
);

Or of course this is much better from your application, like:

$statement = $myDB->prepare('INSERT INTO good_times VALUES (?)');
$statement->execute([$someTime->getTimestamp()]);

Select:

SELECT a_time FROM good_times;

There are techniques for filtering relative times (select posts within the past 30 days, find users that bought within 10 minutes of registering) beyond the scope here.

TIMESTAMP is useful when you have visitors from different countries with different time zones. you can easily convert the TIMESTAMP to any country time zone

A timestamp field is a special case of the datetime field. You can create timestamp columns to have special properties; it can be set to update itself on either create and/or update.

In "bigger" database terms, timestamp has a couple of special-case triggers on it.

What the right one is depends entirely on what you want to do.

Neither. The DATETIME and TIMESTAMP types are fundamentally broken for generic use cases. MySQL will change them in the future. You should use BIGINT and UNIX timestamps unless you have a specific reason to use something else.

Special cases

Here are some specific situations where your choice is easier and you don't need the analysis and general recommendation in this answer.

• Date only — if you only care about the date (like the date of the next Lunar New Year, 2020-02-25) AND you have a clear understanding of what timezone that date applies (or don't care, as in the case of Lunar New Year) then use the DATE column type.

• Record insert times — if you are logging the insert dates/times for rows in your database AND you don't care that your application will break in the next 19 years, then go ahead and use TIMESTAMP with a default value of CURRENT_TIMESTAMP().

Why is TIMESTAMP broken?

The TIMESTAMP type is stored on disk in UTC timezone. This means that if you physically move your server, it does not break. That's good ?. But timestamps as currently defined will stop working entirely in the year 2038 ?.

Every time you INSERT INTO or SELECT FROM a TIMESTAMP column, the physical location (i.e. timezone configuration) of your client/application server is taken into account. If you move your application server then your dates break ?.

Why is DATETIME broken?

A DATETIME stores a DATE and a TIME in the same column. Neither of these things have any meaning unless the timezone is understood, and the timezone is not stored anywhere ?. You should put the intended timezone as a comment in the column because the timezone is inextricably linked to the data. So few people use column comments, therefore this is mistake waiting to happen. I inherited a server from Arizona, so I always need to convert all timestamps FROM Arizona time and then TO another time.

The only situation a DATETIME is correct is to complete this sentence:

Your year 2020 solar new year starts at exactly DATETIME("2020-01-01 00:00:00").

There is no other good use for DATETIMEs. Perhaps you will imagine a web server for a city government in Delaware. Surely the timezone for this server and all the people accessing this server can be implied to be in Delaware, with Eastern Time Zone, right? Wrong! In this millennium, we all think of servers as existing in "the cloud". So it is always wrong to think of your server in any specific timezone, because your server will be moved some day.

Note: MySQL now supports time zone offsets in DATETIME literals (thanks @Marko). This may make inserting DATETIMEs more convenient for you but does not address the incomplete and therefore useless meaning of the data, this fatal issue identifie ("?") above.

How to use BIGINT?

Define:

CREATE TEMPORARY TABLE good_times (
    a_time BIGINT
)

Insert a specific value:

INSERT INTO good_times VALUES (
    UNIX_TIMESTAMP(CONVERT_TZ("2014-12-03 12:24:54", '+00:00', @@global.time_zone))
);

Or of course this is much better from your application, like:

$statement = $myDB->prepare('INSERT INTO good_times VALUES (?)');
$statement->execute([$someTime->getTimestamp()]);

Select:

SELECT a_time FROM good_times;

There are techniques for filtering relative times (select posts within the past 30 days, find users that bought within 10 minutes of registering) beyond the scope here.

The main difference is that DATETIME is constant while TIMESTAMP is affected by the time_zone setting.

So it only matters when you have — or may in the future have — synchronized clusters across time zones.

In simpler words: If I have a database in Australia, and take a dump of that database to synchronize/populate a database in America, then the TIMESTAMP would update to reflect the real time of the event in the new time zone, while DATETIME would still reflect the time of the event in the au time zone.

A great example of DATETIME being used where TIMESTAMP should have been used is in Facebook, where their servers are never quite sure what time stuff happened across time zones. Once I was having a conversation in which the time said I was replying to messages before the message was actually sent. (This, of course, could also have been caused by bad time zone translation in the messaging software if the times were being posted rather than synchronized.)

Depends on application, really.

Consider setting a timestamp by a user to a server in New York, for an appointment in Sanghai. Now when the user connects in Sanghai, he accesses the same appointment timestamp from a mirrored server in Tokyo. He will see the appointment in Tokyo time, offset from the original New York time.

So for values that represent user time like an appointment or a schedule, datetime is better. It allows the user to control the exact date and time desired, regardless of the server settings. The set time is the set time, not affected by the server's time zone, the user's time zone, or by changes in the way daylight savings time is calculated (yes it does change).

On the other hand, for values that represent system time like payment transactions, table modifications or logging, always use timestamps. The system will not be affected by moving the server to another time zone, or when comparing between servers in different timezones.

Timestamps are also lighter on the database and indexed faster.

I would always use a Unix timestamp when working with MySQL and PHP. The main reason for this being the default date method in PHP uses a timestamp as the parameter, so there would be no parsing needed.

To get the current Unix timestamp in PHP, just do time();
and in MySQL do SELECT UNIX_TIMESTAMP();.

I stopped using datetime in my applications after facing many problems and bugs related to time zones. IMHO using timestamp is better than datetime in most of the cases.

When you ask what is the time ? and the answer comes as something like '2019-02-05 21:18:30', that is not completed, not defined answer because it lacks another part, in which timezone ? Washington ? Moscow ? Beijing ?

Using datetimes without the timezone means that your application is dealing with only 1 timezone, however timestamps give you the benefits of datetime plus the flexibility of showing the same exact point of time in different timezones.

Here are some cases that will make you regret using datetime and wish that you stored your data in timestamps.

1. For your clients comfort you want to show them the times based on their preferred time zones without making them doing the math and convert the time to their meaningful timezone. all you need is to change the timezone and all your application code will be the same.(Actually you should always define the timezone at the start of the application, or request processing in case of PHP applications)

   SET time_zone = '+2:00';
   

2. you changed the country you stay in, and continue your work of maintaining the data while seeing it in a different timezone (without changing the actual data).

3. you accept data from different clients around the world, each of them inserts the time in his timezone.

In short

datetime = application supports 1 timezone (for both inserting and selecting)

timestamp = application supports any timezone (for both inserting and selecting)

This answer is only for putting some highlight on the flexibility and ease of timestamps when it comes to time zones , it is not covering any other differences like the column size or range or fraction.

I prefer using timestamp so to keep everything in one common raw format and format the data in PHP code or in your SQL query. There are instances where it comes in handy in your code to keep everything in plain seconds.

The major difference is

• a INDEX's on Timestamp - works
• a INDEX's on Datetime - Does not work

look at this post to see problems with Datetime indexing

I always use DATETIME fields for anything other than row metadata (date created or modified).

As mentioned in the MySQL documentation:

The DATETIME type is used when you need values that contain both date and time information. MySQL retrieves and displays DATETIME values in 'YYYY-MM-DD HH:MM:SS' format. The supported range is '1000-01-01 00:00:00' to '9999-12-31 23:59:59'.

...

The TIMESTAMP data type has a range of '1970-01-01 00:00:01' UTC to '2038-01-09 03:14:07' UTC. It has varying properties, depending on the MySQL version and the SQL mode the server is running in.

You're quite likely to hit the lower limit on TIMESTAMPs in general use -- e.g. storing birthdate.

DATETIME vs TIMESTAMP:

TIMESTAMP used to track changes of records, and update every time when the record is changed.

DATETIME used to store specific and static value which is not affected by any changes in records.

TIMESTAMP also affected by different TIME ZONE related setting. DATETIME is constant.

TIMESTAMP internally converted a current time zone to UTC for storage, and during retrieval convert the back to the current time zone.

DATETIME can not do this.

TIMESTAMP is 4 bytes and DATETIME is 8 bytes.

TIMESTAMP supported range: ‘1970-01-01 00:00:01' UTC to ‘2038-01-19 03:14:07' UTC DATETIME supported range: ‘1000-01-01 00:00:00' to ‘9999-12-31 23:59:59'

Another difference between Timestamp and Datetime is in Timestamp you can't default value to NULL.

A DATETIME carries no timezone information with it and will always display the same independent of the timezone that is in effect for the session, which defaults to the server's timezone unless you have explicitly changed it. However, if I initialize a DATETIME column with a function such as NOW() rather than a literal such as '2020-01-16 12:15:00', then the value stored will, of course, be the current date and time localized to the session's timezone.

A TIMESTAMP by contrast does implicitly carry timezone information: When you initialize a TIMESTAMP column with a value, that value is converted to UTC before it is stored. If the value being stored is a literal such as '2020-01-16 12:15:00', it is interpreted as being in the session's current timezone for conversion purposes. Conversely, when a TIMESTAMP column is displayed, it will first be converted from UTC to the session's current timezone.

When to use one or the other? A Case Study

A Website for a community theater group is presenting several performances of a play for which it is selling tickets. The dates and times of these performances will appear in a drop down from which a customer wishing to buy tickets for a performance will select one. It would make sense for database column performance_date_and_time to be a DATETIME type. If the performance is in New York, there is an understanding that there is an implicit timezone involved ("New York local time") and ideally we would want the date and time to display as 'December 12, 2019 at 8:00 PM' regardless of the session's timezone and without having to go to the trouble of having to do any timezone conversions.

On the other hand, once the December 12th, 2019 8 PM performance began, we might no longer want to sell tickets for it and thus no longer display that performance in the drop down. So, we would like to be able to know whether '2019-12-12 20:00:00' has occurred or not. That would argue for having a TIMESTAMP column, setting the timezone for the session to 'America/New_York' with set session time_zone='America/New_York' and then storing '2019-12-12 20:00:00' into the TIMESTAMP column. Henceforth we can test for whether the performance has begun by comparing this column with NOW() independent of the current session timezone.

Or it might make sense to have a DATETIME and a TIMESTAMP column for these two separate purposes. Or not. Clearly, either one could serve both purposes. If you go with just a DATETIME column, then you must set the current timezone to your local timezone before comparing with NOW(). If you go with just a TIMESTAMP column, you must set the session timezone to your local timezone before displaying the column.

I always use DATETIME fields for anything other than row metadata (date created or modified).

As mentioned in the MySQL documentation:

The DATETIME type is used when you need values that contain both date and time information. MySQL retrieves and displays DATETIME values in 'YYYY-MM-DD HH:MM:SS' format. The supported range is '1000-01-01 00:00:00' to '9999-12-31 23:59:59'.

...

The TIMESTAMP data type has a range of '1970-01-01 00:00:01' UTC to '2038-01-09 03:14:07' UTC. It has varying properties, depending on the MySQL version and the SQL mode the server is running in.

You're quite likely to hit the lower limit on TIMESTAMPs in general use -- e.g. storing birthdate.

I merely use unsigned BIGINT while storing UTC ...

which then still can be adjusted to local time in PHP.

the DATETIME to be selected with FROM_UNIXTIME( integer_timestamp_column ).

one obviously should set an index on that column, else there would be no advance.

Depends on application, really.

Consider setting a timestamp by a user to a server in New York, for an appointment in Sanghai. Now when the user connects in Sanghai, he accesses the same appointment timestamp from a mirrored server in Tokyo. He will see the appointment in Tokyo time, offset from the original New York time.

So for values that represent user time like an appointment or a schedule, datetime is better. It allows the user to control the exact date and time desired, regardless of the server settings. The set time is the set time, not affected by the server's time zone, the user's time zone, or by changes in the way daylight savings time is calculated (yes it does change).

On the other hand, for values that represent system time like payment transactions, table modifications or logging, always use timestamps. The system will not be affected by moving the server to another time zone, or when comparing between servers in different timezones.

Timestamps are also lighter on the database and indexed faster.

Reference taken from this Article:

The main differences:

TIMESTAMP used to track changes to records, and update every time when the record is changed. DATETIME used to store specific and static value which is not affected by any changes in records.

TIMESTAMP also affected by different TIME ZONE related setting. DATETIME is constant.

TIMESTAMP internally converted current time zone to UTC for storage, and during retrieval converted back to the current time zone. DATETIME can not do this.

TIMESTAMP supported range: ‘1970-01-01 00:00:01' UTC to ‘2038-01-19 03:14:07' UTC DATETIME supported range: ‘1000-01-01 00:00:00' to ‘9999-12-31 23:59:59'

I would always use a Unix timestamp when working with MySQL and PHP. The main reason for this being the default date method in PHP uses a timestamp as the parameter, so there would be no parsing needed.

To get the current Unix timestamp in PHP, just do time();
and in MySQL do SELECT UNIX_TIMESTAMP();.

I prefer using timestamp so to keep everything in one common raw format and format the data in PHP code or in your SQL query. There are instances where it comes in handy in your code to keep everything in plain seconds.

A TIMESTAMP requires 4 bytes, whereas a DATETIME requires 8 bytes.

If you want to GUARANTEE your application will NOT function in February, 2038, use TIMESTAMP. Refer to your REFMAN for the RANGE of dates supported.

I prefer using timestamp so to keep everything in one common raw format and format the data in PHP code or in your SQL query. There are instances where it comes in handy in your code to keep everything in plain seconds.

I would always use a Unix timestamp when working with MySQL and PHP. The main reason for this being the default date method in PHP uses a timestamp as the parameter, so there would be no parsing needed.

To get the current Unix timestamp in PHP, just do time();
and in MySQL do SELECT UNIX_TIMESTAMP();.

In my case, I set UTC as a time zone for everything: the system, the database server, etc. every time that I can. If my customer requires another time zone, then I configure it on the app.

I almost always prefer timestamps rather than datetime fields, because timestamps include the timezone implicitly. So, since the moment that the app will be accessed from users from different time zones and you want them to see dates and times in their local timezone, this field type makes it pretty easy to do it than if the data were saved in datetime fields.

As a plus, in the case of a migration of the database to a system with another timezone, I would feel more confident using timestamps. Not to say possible issues when calculating differences between two moments with a sumer time change in between and needing a precision of 1 hour or less.

So, to summarize, I value this advantages of timestamp:

• ready to use on international (multi time zone) apps
• easy migrations between time zones
• pretty easy to calculate diferences (just subtract both timestamps)
• no worry about dates in/out a summer time period

For all this reasons, I choose UTC & timestamp fields where posible. And I avoid headaches ;)

DATETIME vs TIMESTAMP:

TIMESTAMP used to track changes of records, and update every time when the record is changed.

DATETIME used to store specific and static value which is not affected by any changes in records.

TIMESTAMP also affected by different TIME ZONE related setting. DATETIME is constant.

TIMESTAMP internally converted a current time zone to UTC for storage, and during retrieval convert the back to the current time zone.

DATETIME can not do this.

TIMESTAMP is 4 bytes and DATETIME is 8 bytes.

TIMESTAMP supported range: ‘1970-01-01 00:00:01' UTC to ‘2038-01-19 03:14:07' UTC DATETIME supported range: ‘1000-01-01 00:00:00' to ‘9999-12-31 23:59:59'

TIMESTAMP is useful when you have visitors from different countries with different time zones. you can easily convert the TIMESTAMP to any country time zone

I stopped using datetime in my applications after facing many problems and bugs related to time zones. IMHO using timestamp is better than datetime in most of the cases.

When you ask what is the time ? and the answer comes as something like '2019-02-05 21:18:30', that is not completed, not defined answer because it lacks another part, in which timezone ? Washington ? Moscow ? Beijing ?

Using datetimes without the timezone means that your application is dealing with only 1 timezone, however timestamps give you the benefits of datetime plus the flexibility of showing the same exact point of time in different timezones.

Here are some cases that will make you regret using datetime and wish that you stored your data in timestamps.

1. For your clients comfort you want to show them the times based on their preferred time zones without making them doing the math and convert the time to their meaningful timezone. all you need is to change the timezone and all your application code will be the same.(Actually you should always define the timezone at the start of the application, or request processing in case of PHP applications)

   SET time_zone = '+2:00';
   

2. you changed the country you stay in, and continue your work of maintaining the data while seeing it in a different timezone (without changing the actual data).

3. you accept data from different clients around the world, each of them inserts the time in his timezone.

In short

datetime = application supports 1 timezone (for both inserting and selecting)

timestamp = application supports any timezone (for both inserting and selecting)

This answer is only for putting some highlight on the flexibility and ease of timestamps when it comes to time zones , it is not covering any other differences like the column size or range or fraction.

I always use DATETIME fields for anything other than row metadata (date created or modified).

As mentioned in the MySQL documentation:

The DATETIME type is used when you need values that contain both date and time information. MySQL retrieves and displays DATETIME values in 'YYYY-MM-DD HH:MM:SS' format. The supported range is '1000-01-01 00:00:00' to '9999-12-31 23:59:59'.

...

The TIMESTAMP data type has a range of '1970-01-01 00:00:01' UTC to '2038-01-09 03:14:07' UTC. It has varying properties, depending on the MySQL version and the SQL mode the server is running in.

You're quite likely to hit the lower limit on TIMESTAMPs in general use -- e.g. storing birthdate.

I found unsurpassed usefulness in TIMESTAMP's ability to auto update itself based on the current time without the use of unnecessary triggers. That's just me though, although TIMESTAMP is UTC like it was said.

It can keep track across different timezones, so if you need to display a relative time for instance, UTC time is what you would want.

Another difference between Timestamp and Datetime is in Timestamp you can't default value to NULL.

Reference taken from this Article:

The main differences:

TIMESTAMP used to track changes to records, and update every time when the record is changed. DATETIME used to store specific and static value which is not affected by any changes in records.

TIMESTAMP also affected by different TIME ZONE related setting. DATETIME is constant.

TIMESTAMP internally converted current time zone to UTC for storage, and during retrieval converted back to the current time zone. DATETIME can not do this.

TIMESTAMP supported range: ‘1970-01-01 00:00:01' UTC to ‘2038-01-19 03:14:07' UTC DATETIME supported range: ‘1000-01-01 00:00:00' to ‘9999-12-31 23:59:59'

A timestamp field is a special case of the datetime field. You can create timestamp columns to have special properties; it can be set to update itself on either create and/or update.

In "bigger" database terms, timestamp has a couple of special-case triggers on it.

What the right one is depends entirely on what you want to do.

It is worth noting in MySQL you can use something along the lines of the below when creating your table columns:

on update CURRENT_TIMESTAMP

This will update the time at each instance you modify a row and is sometimes very helpful for stored last edit information. This only works with timestamp, not datetime however.