Convert LocalDateTime to LocalDateTime in UTC

Question

Convert LocalDateTime to LocalDateTime in UTC   LocalDateTime convertToUtc LocalDateTime date           do conversion      I searched over net  But did not get a solution

User · Answer

LocalDateTime does not contain Zone information. ZonedDatetime does.

If you want to convert LocalDateTime to UTC, you need to wrap by ZonedDateTime fist.

You can convert like the below.

LocalDateTime ldt = LocalDateTime.now();
System.out.println(ldt.toLocalTime());

ZonedDateTime ldtZoned = ldt.atZone(ZoneId.systemDefault());

ZonedDateTime utcZoned = ldtZoned.withZoneSameInstant(ZoneId.of("UTC"));

System.out.println(utcZoned.toLocalTime());

User · Answer

There is an even simpler way  LocalDateTime now Clock systemUTC

User · Answer

Try this using this method  convert your LocalDateTime to ZonedDateTime by using the of method and pass system default time zone or you can use ZoneId of your zone like ZoneId of  quot Australia Sydney quot    LocalDateTime convertToUtc LocalDateTime dateTime      ZonedDateTime dateTimeInMyZone   ZonedDateTime                                          of dateTime  ZoneId systemDefault        return dateTimeInMyZone                    withZoneSameInstant ZoneOffset UTC                     toLocalDateTime          To convert back to your zone local date time use  LocalDateTime convertFromUtc LocalDateTime utcDateTime       return ZonedDateTime              of utcDateTime  ZoneId of  quot UTC quot                 toOffsetDateTime                atZoneSameInstant ZoneId systemDefault                 toLocalDateTime

User · Answer

tldr  there is simply no way to do that  if you are trying to do that  you get LocalDateTime wrong   The reason is that LocalDateTime does not record Time Zone after instances are created  You cannot convert a date time without time zone to another date time based on a specific time zone   As a matter of fact  LocalDateTime now   should never be called in production code unless your purpose is getting random results  When you construct a LocalDateTime instance like that  this instance contains date time ONLY based on current server s time zone  which means this piece of code will generate different result if it is running a server with a different time zone config   LocalDateTime can simplify date calculating  If you want a real universally usable data time  use ZonedDateTime or OffsetDateTime  https   docs oracle com javase 8 docs api java time OffsetDateTime html

User · Answer

Question   Looking at the answers and the question  it seems the question has been modified significantly  So to answer the current question      Convert LocalDateTime to LocalDateTime in UTC    Timezone   LocalDateTime does not store any information about the time-zone  it just basically holds the values of year  month  day  hour  minute  second  and smaller units  So an important question is  What is the timezone of the original LocalDateTime  It might as well be UTC already  therefore no conversion has to be made   System Default Timezone  Considering that you asked the question anyway  you probably meant that the original time is in your system-default timezone and you want to convert it to UTC  Because usually a LocalDateTime object is created by using LocalDateTime now   which returns the current time in the system-default timezone  In this case  the conversion would be the following   LocalDateTime convertToUtc LocalDateTime time        return time atZone ZoneId systemDefault    withZoneSameInstant ZoneOffset UTC  toLocalDateTime        An example of the conversion process   2019-02-25 11 39     time  original LocalDateTime without a timezone 2019-02-25 11 39 GMT 1     atZone  converted to ZonedDateTime  system timezone is Madrid  2019-02-25 10 39 GMT     withZoneSameInstant  converted to UTC  still as ZonedDateTime 2019-02-25 10 39     toLocalDateTime  losing the timezone information   Explicit Timezone  In any other case  when you explicitly specify the timezone of the time to convert  the conversion would be the following   LocalDateTime convertToUtc LocalDateTime time  ZoneId zone        return time atZone zone  withZoneSameInstant ZoneOffset UTC  toLocalDateTime        An example of the conversion process   2019-02-25 11 39     time  original LocalDateTime without a timezone 2019-02-25 11 39 GMT 2     atZone  converted to ZonedDateTime  zone is Europe Tallinn  2019-02-25 09 39 GMT     withZoneSameInstant  converted to UTC  still as ZonedDateTime 2019-02-25 09 39     toLocalDateTime  losing the timezone information   The atZone   Method  The result of the atZone   method depends on the time passed as its argument  because it considers all the rules of the timezone  including Daylight Saving Time  DST   In the examples  the time was 25th February  in Europe this means winter time  no DST    If we were to use a different date  let s say 25th August from last year  the result would be different  considering DST   2018-08-25 11 39     time  original LocalDateTime without a timezone 2018-08-25 11 39 GMT 3     atZone  converted to ZonedDateTime  zone is Europe Tallinn  2018-08-25 08 39 GMT     withZoneSameInstant  converted to UTC  still as ZonedDateTime 2018-08-25 08 39     toLocalDateTime  losing the timezone information   The GMT time does not change  Therefore the offsets in the other timezones are adjusted  In this example  the summer time of Estonia is GMT 3  and winter time GMT 2   Also  if you specify a time within the transition of changing clocks back one hour  E g  October 28th  2018 03 30 for Estonia  this can mean two different times   2018-10-28 03 30 GMT 3    summer time  UTC 2018-10-28 00 30  2018-10-28 04 00 GMT 3    clocks are turned back 1 hour  UTC 2018-10-28 01 00  2018-10-28 03 00 GMT 2    same as above  UTC 2018-10-28 01 00  2018-10-28 03 30 GMT 2    winter time  UTC 2018-10-28 01 30    Without specifying the offset manually  GMT 2 or GMT 3   the time 03 30 for the timezone Europe Tallinn can mean two different UTC times  and two different offsets   Summary  As you can see  the end result depends on the timezone of the time passed as an argument  Because the timezone cannot be extracted from the LocalDateTime object  you have to know yourself which timezone it is coming from in order to convert it to UTC

User · Answer

Here s a simple little utility class that you can use to convert local date times from zone to zone  including a utility method directly to convert a local date time from the current zone to UTC  with main method so you can run it and see the results of a simple test    import java time LocalDateTime  import java time ZoneId  import java time ZoneOffset  import java time ZonedDateTime   public final class DateTimeUtil       private DateTimeUtil             super               public static void main final String    args            final LocalDateTime now   LocalDateTime now            final LocalDateTime utc   DateTimeUtil toUtc now            System out println  Now      now           System out println  UTC      utc              public static LocalDateTime toZone final LocalDateTime time  final ZoneId fromZone  final ZoneId toZone            final ZonedDateTime zonedtime   time atZone fromZone           final ZonedDateTime converted   zonedtime withZoneSameInstant toZone           return converted toLocalDateTime               public static LocalDateTime toZone final LocalDateTime time  final ZoneId toZone            return DateTimeUtil toZone time  ZoneId systemDefault    toZone              public static LocalDateTime toUtc final LocalDateTime time  final ZoneId fromZone            return DateTimeUtil toZone time  fromZone  ZoneOffset UTC              public static LocalDateTime toUtc final LocalDateTime time            return DateTimeUtil toUtc time  ZoneId systemDefault

User · Answer

Use the below  It takes the local datetime and converts it to UTC using the timezone  You do not need to create it function   ZonedDateTime nowUTC   ZonedDateTime now ZoneOffset UTC   System out println nowUTC toString       If you need to obtain the LocalDateTime part of the ZonedDateTime then you can use the following   nowUTC toLocalDateTime      Here is a static method i use in my application to insert UTC time in mysql since i cannot add a default value UTC TIMESTAMP to a datetime column   public static LocalDateTime getLocalDateTimeInUTC        ZonedDateTime nowUTC   ZonedDateTime now ZoneOffset UTC        return nowUTC toLocalDateTime

User · Answer

I personally prefer   LocalDateTime now ZoneOffset UTC     as it is the most readable option

User · Answer

public static String convertFromGmtToLocal String gmtDtStr  String dtFormat  TimeZone lclTimeZone  throws Exception          if  gmtDtStr    null    gmtDtStr trim   equals      return null          SimpleDateFormat format   new SimpleDateFormat dtFormat           format setTimeZone getGMTTimeZone             Date dt   format parse gmtDtStr           format setTimeZone lclTimeZone           return   format format dt

User · Answer

you can implement a helper doing something like that      public static LocalDateTime convertUTCFRtoUTCZ LocalDateTime dateTime        ZoneId fr   ZoneId of  Europe Paris        ZoneId utcZ   ZoneId of  Z        ZonedDateTime frZonedTime   ZonedDateTime of dateTime  fr       ZonedDateTime utcZonedTime   frZonedTime withZoneSameInstant utcZ       return utcZonedTime toLocalDateTime

[java] Convert LocalDateTime to LocalDateTime in UTC

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