How to Convert Between Java 8 LocalDateTime and java.util.Date?

Converting Between Java 8 LocalDateTime and java.util.Date

Converting from java.util.Date to LocalDateTime:

To convert a java.util.Date object to a LocalDateTime, first convert the Date to an Instant using its toInstant() method:

Date in = new Date();
Instant instant = in.toInstant();

Then create a LocalDateTime object using LocalDateTime.ofInstant(), specifying the desired time zone:

LocalDateTime ldt = LocalDateTime.ofInstant(instant, ZoneId.systemDefault());

Converting from LocalDateTime to java.util.Date:

To convert a LocalDateTime back to a java.util.Date, first convert it to an Instant using its atZone() and toInstant() methods:

LocalDateTime ldt = ...
ZonedDateTime zdt = ldt.atZone(ZoneId.systemDefault());
Instant instant = zdt.toInstant();

Finally, create a new java.util.Date object from the Instant:

Date out = Date.from(instant);

Considerations:

• The conversion from LocalDateTime to ZonedDateTime may result in unexpected behavior due to Daylight Saving Time.
• Round-tripping between java.util.Date and LocalDateTime may result in a different instant due to Daylight Saving Time.
• java.time.* uses the ISO calendar system for all dates, while java.util.Date uses the Gregorian calendar after October 15, 1582, and the Julian calendar before that.

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