Get timezone from DateTime

Question

Does the  Net DateTime contain information about time zone where it was created    I have a library parsing DateTime from a format that has   zz  at the end  and while it parses correctly and adjusts a local time  I need to get what the specific time zone was from the DateTime object    Is this possible at all  All I can see is DateTime Kind  which specifies if time is local or UTC

User · Answer

DateTime does not know its timezone offset. There is no built-in method to return the offset or the timezone name (e.g. EAT, CEST, EST etc).

Like suggested by others, you can convert your date to UTC:

DateTime localtime = new DateTime.Now;
var utctime = localtime.ToUniversalTime();

and then only calculate the difference:

TimeSpan difference = localtime - utctime;

Also you may convert one time to another by using the DateTimeOffset:

DateTimeOffset targetTime = DateTimeOffset.Now.ToOffset(new TimeSpan(5, 30, 0));

But this is sort of lossy compression - the offset alone cannot tell you which time zone it is as two different countries may be in different time zones and have the same time only for part of the year (eg. South Africa and Europe). Also, be aware that summer daylight saving time may be introduced at different dates (EST vs CET - a 3-week difference).

You can get the name of your local system time zone using TimeZoneInfo class:

TimeZoneInfo localZone = TimeZoneInfo.Local;
localZone.IsDaylightSavingTime(localtime) ? localZone.DaylightName : localZone.StandardName

I agree with Gerrie Schenck, please read the article he suggested.

User · Answer

There is a public domain TimeZone library for  NET   Really useful   It will answer your needs   Solving the general-case timezone problem is harder than you think

User · Answer

DateTime itself contains no real timezone information  It may know if it s UTC or local  but not what local really means   DateTimeOffset is somewhat better - that s basically a UTC time and an offset  However  that s still not really enough to determine the timezone  as many different timezones can have the same offset at any one point in time  This sounds like it may be good enough for you though  as all you ve got to work with when parsing the date time is the offset    The support for time zones as of  NET 3 5 is a lot better than it was  but I d really like to see a standard  ZonedDateTime  or something like that - a UTC time and an actual time zone  It s easy to build your own  but it would be nice to see it in the standard libraries   EDIT  Nearly four years later  I d now suggest using Noda Time which has a rather richer set of date time types  I m biased though  as the main author of Noda Time

User · Answer

From the API  http   msdn microsoft com en-us library system datetime members VS 71  aspx  it does not seem it can show the name of the time zone used

User · Answer

Generally the practice would be to pass data as a DateTime with a  timezone  of UTC and then pass a TimeZoneInfo object and when you are ready to display the data  you use the TimeZoneInfo object to convert the UTC DateTime   The other option is to set the DateTime with the current timezone  and then make sure the  timezone  is unknown for the DateTime object  then make sure the DateTime is again passed with a TimeZoneInfo that indicates the TimeZone of the DateTime passed   As others have indicated here  it would be nice if Microsoft got on top of this and created one nice object to do it all  but for now you have to deal with two objects

User · Answer

No      A developer is responsible for keeping track of time-zone information associated with a DateTime value via some external mechanism    A quote from an excellent article here  A must read for every  Net developer   So my advice is to write a little wrapper class that suits your needs

User · Answer

You could use TimeZoneInfo class  The TimeZone class recognizes local time zone  and can convert times between Coordinated Universal Time  UTC  and local time  A TimeZoneInfo object can represent any time zone  and methods of the TimeZoneInfo class can be used to convert the time in one time zone to the corresponding time in any other time zone  The members of the TimeZoneInfo class support the following operations    Retrieving a time zone that is already defined by the operating system  Enumerating the time zones that are available on a system  Converting times between different time zones  Creating a new time zone that is not already defined by the operating system   Serializing a time zone for later retrieval

[c#] Get timezone from DateTime

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