How to extract epoch from LocalDate and LocalDateTime

Question

How do I extract the epoch value to Long from instances of LocalDateTime or LocalDate  I ve tried  the following  but it gives me other results   LocalDateTime time   LocalDateTime parse  04 02 2014  19 51 01   DateTimeFormatter ofPattern  dd MM yyyy  HH mm ss     System out println time getLong ChronoField SECOND OF DAY       gives 71461 System out println time getLong ChronoField EPOCH DAY       gives 16105   What I want is simply the value 1391539861 for the local datetime  04 02 2014  19 51 01   My timezone is Europe Oslo UTC 1 with daylight saving time

User · Answer

Convert from human readable date to epoch   long epoch   new java text SimpleDateFormat  MM dd yyyyHH mm ss   parse  01 01 1970 01 00 00   getTime     1000    Convert from epoch to human readable date   String date   new java text SimpleDateFormat  MM dd yyyyHH mm ss   format new java util Date  epoch 1000      For other language converter  https   www epochconverter com

User · Answer

The classes LocalDate and LocalDateTime do not contain information about the timezone or time offset  and seconds since epoch would be ambigious without this information  However  the objects have several methods to convert them into date time objects with timezones by passing a ZoneId instance   LocalDate  LocalDate date        ZoneId zoneId   ZoneId systemDefault       or  ZoneId of  Europe Oslo    long epoch   date atStartOfDay zoneId  toEpochSecond      LocalDateTime  LocalDateTime time        ZoneId zoneId   ZoneId systemDefault       or  ZoneId of  Europe Oslo    long epoch   time atZone zoneId  toEpochSecond

User · Answer

The conversion you need requires the offset from UTC Greewich  or a time-zone   If you have an offset  there is a dedicated method on LocalDateTime for this task   long epochSec   localDateTime toEpochSecond zoneOffset     If you only have a ZoneId then you can obtain the ZoneOffset from the ZoneId   ZoneOffset zoneOffset   ZoneId of  Europe Oslo   getRules   getOffset ldt     But you may find conversion via ZonedDateTime simpler   long epochSec   ldt atZone zoneId  toEpochSecond

User · Answer

This is one way without using time a zone    LocalDateTime now   LocalDateTime now    long epoch    now getLong ChronoField EPOCH DAY    86400000    now getLong ChronoField MILLI OF DAY

User · Answer

Look at this method to see which fields are supported  You will find for LocalDateTime      NANO OF SECOND     NANO OF DAY     MICRO OF SECOND     MICRO OF DAY     MILLI OF SECOND     MILLI OF DAY     SECOND OF MINUTE     SECOND OF DAY     MINUTE OF HOUR     MINUTE OF DAY     HOUR OF AMPM     CLOCK HOUR OF AMPM     HOUR OF DAY     CLOCK HOUR OF DAY     AMPM OF DAY     DAY OF WEEK     ALIGNED DAY OF WEEK IN MONTH     ALIGNED DAY OF WEEK IN YEAR     DAY OF MONTH     DAY OF YEAR     EPOCH DAY     ALIGNED WEEK OF MONTH     ALIGNED WEEK OF YEAR     MONTH OF YEAR     PROLEPTIC MONTH     YEAR OF ERA     YEAR     ERA    The field INSTANT SECONDS is - of course - not supported because a LocalDateTime cannot refer to any absolute  global  timestamp  But what is helpful is the field EPOCH DAY which counts the elapsed days since 1970-01-01  Similar thoughts are valid for the type LocalDate  with even less supported fields    If you intend to get the non-existing millis-since-unix-epoch field you also need the timezone for converting from a local to a global type  This conversion can be done much simpler  see other SO-posts   Coming back to your question and the numbers in your code   The result 1605 is correct     gt   2014 - 1970    365   11  leap days    31  in january 2014    3  in february 2014  The result 71461 is also correct   gt  19   3600   51   60   1   16105L   86400   71461   1391543461 seconds since 1970-01-01T00 00 00  attention  no timezone  Then you can subtract the timezone offset  watch out for possible multiplication by 1000 if in milliseconds    UPDATE after given timezone info   local time   1391543461 secs offset   3600 secs  Europe Oslo  winter time in february  utc   1391543461 - 3600   1391539861   As JSR-310-code with two equivalent approaches   long secondsSinceUnixEpoch1     LocalDateTime of 2014  2  4  19  51  1  atZone ZoneId of  Europe Oslo    toEpochSecond     long secondsSinceUnixEpoch2     LocalDate      of 2014  2  4       atTime 19  51  1       atZone ZoneId of  Europe Oslo         toEpochSecond

User · Answer

Millis since unix epoch  represents an instant  so you should use the Instant class   private long toEpochMilli LocalDateTime localDateTime      return localDateTime atZone ZoneId systemDefault         toInstant   toEpochMilli

[java] How to extract epoch from LocalDate and LocalDateTime?

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