Convert timestamp long to normal date format

Question

In my web app  date  amp  time of a user s certain activity is stored in database  as a timestamp Long which on being displayed back to user needs to be converted into normal date time format     Actually my database Cassandra stores the timestamp of when a column was written to it  as a long value  microseconds since 1970   which I will use to find out the time of that corresponding user activity   I am using JSF 2 0   primefaces  which I believe has converters that may be helpful for this conversion  Or otherwise how How can I  at best  achieve these conversions

User · Accepted Answer

Let me propose this solution for you  So in your managed bean  do this  public String convertTime long time       Date date   new Date time       Format format   new SimpleDateFormat  yyyy MM dd HH mm ss        return format format date       so in your JSF page  you can do this  assuming foo is the object that contain your time    lt h dataTable value    myBean convertTime myBean foo time      gt    If you have multiple pages that want to utilize this method  you can put this in an abstract class and have your managed bean extend this abstract class    EDIT  Return time with TimeZone  unfortunately  I think SimpleDateFormat will always format the time in local time  so we can t use SimpleDateFormat anymore  So to display time in different TimeZone  we can do this  public String convertTimeWithTimeZome long time       Calendar cal   Calendar getInstance        cal setTimeZone TimeZone getTimeZone  UTC         cal setTimeInMillis time       return  cal get Calendar YEAR           cal get Calendar MONTH    1                       cal get Calendar DAY OF MONTH          cal get Calendar HOUR OF DAY                      cal get Calendar MINUTE         A better solution is to utilize JodaTime  In my opinion  this API is much better than Calendar  lighter weight  faster and provide more functionality   Plus Calendar Month of January is 0  that force developer to add 1 to the result  and you have to format the time yourself  Using JodaTime  you can fix all of that  Correct me if I am wrong  but I think JodaTime is incorporated in JDK7

User · Answer

To show leading zeros infront of hours  minutes and seconds use below modified code  The trick here is we are converting  or more accurately formatting  integer into string so that it shows leading zero whenever applicable     public String convertTimeWithTimeZome long time            Calendar cal   Calendar getInstance            cal setTimeZone TimeZone getTimeZone  UTC             cal setTimeInMillis time           String curTime   String format   02d  02d  02d   cal get Calendar HOUR OF DAY   cal get Calendar MINUTE   cal get Calendar SECOND            return curTime          Result would be like   00 01 30

User · Answer

Not sure if JSF provides a built-in functionality  but you could use java sql Date s constructor to convert to a date object  http   download oracle com javase 1 5 0 docs api java sql Date html Date long   Then you should be able to use higher level features provided by Java SE  Java EE to display and format the extracted date  You could instantiate a java util Calendar and explicitly set the time  http   download oracle com javase 1 5 0 docs api java util Calendar html setTime java util Date   EDIT  The JSF components should not take care of the conversion  Your data access layer  persistence layer  should take care of this  In other words  your JSF components should not handle the long typed attributes but only a Date or Calendar typed attributes

User · Answer

java time      ZoneId usersTimeZone   ZoneId of  Asia Tashkent        Locale usersLocale   Locale forLanguageTag  ga-IE        DateTimeFormatter formatter   DateTimeFormatter ofLocalizedDateTime FormatStyle MEDIUM               withLocale usersLocale        long microsSince1970   1 512 345 678 901 234L      long secondsSince1970   TimeUnit MICROSECONDS toSeconds microsSince1970       long remainingMicros   microsSince1970 - TimeUnit SECONDS toMicros secondsSince1970       ZonedDateTime dateTime   Instant ofEpochSecond secondsSince1970                       TimeUnit MICROSECONDS toNanos remainingMicros                atZone usersTimeZone       String dateTimeInUsersFormat   dateTime format formatter       System out println dateTimeInUsersFormat     The above snippet prints      4 Noll 2017 05 01 18      Noll    is Gaelic for December  so this should make your user happy  Except there may be very few Gaelic speaking people living in Tashkent  so please specify the user   s correct time zone and locale yourself   I am taking seriously that you got microseconds from your database  If second precision is fine  you can do without remainingMicros and just use the one-arg Instant ofEpochSecond    which will make the code a couple of lines shorter  Since Instant and ZonedDateTime do support nanosecond precision  I found it most correct to keep the full precision of your timestamp  If your timestamp was in milliseconds rather than microseconds  which they often are   you may just use Instant ofEpochMilli     The answers using Date  Calendar and or SimpleDateFormat were fine when this question was asked 7 years ago  Today those classes are all long outdated  and we have so much better in java time  the modern Java date and time API   For most uses I recommend you use the built-in localized formats as I do in the code  You may experiment with passing SHORT  LONG or FULL for format style  Yo may even specify format style for the date and for the time of day separately using an overloaded ofLocalizedDateTime method  If a specific format is required  this was asked in a duplicate question   you can have that       DateTimeFormatter formatter   DateTimeFormatter ofPattern  HH mm ss  dd MM uuuu      Using this formatter instead we get     05 01 18  04 12 2017   Link  Oracle tutorial  Date Time explaining how to use java time

User · Answer

I tried this and worked for me   Date    long  DateTime Now Subtract new DateTime 1970  1  1  0  0  0    TotalSeconds

[java] Convert timestamp long to normal date format

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