Transforming OffsetDateTime to LocalDateTime to store in DB

At this moment, my preferred approach is handling all dates on the app as OffsetDataTime, on this way we preserve the instant no matter the Offset and then transform this to UTC when it’s going to be stored, later, when recovering the value from the persistence mechanism (DB), read it directly as OffsetDateTime or read it as LocalDateTime and transform it to OffsetDateTime with offset on UTC.

This transformation can be done using the method withOffsetSameInstant(ZoneOffset.UTC) from OffsetDateTime and the method .atOffset(ZoneOffset.UTC) from LocalDateTime.

@Test
@DisplayName("reviewing offset datetime transformations")
void reviewingOffsetDatetimeTransformations() {
  // The default offset in my location is +01:00
  Clock clock = Clock.fixed(Instant.now(), ZoneId.systemDefault());
  OffsetDateTime offsetDateTime = OffsetDateTime.now(clock);
  
  var utcOffSet = offsetDateTime.withOffsetSameInstant(ZoneOffset.UTC);
  var localFromOffset = utcOffSet.toLocalDateTime();
  var offsetFromLocal = localFromOffset.atOffset(ZoneOffset.UTC);

  System.out.println(offsetDateTime);
  System.out.println(utcOffSet);
  System.out.println(localFromOffset);
  System.out.println(offsetFromLocal);

  assertThat(offsetDateTime)
    .isEqualTo(utcOffSet)
    .isEqualTo(offsetFromLocal);
}

With above test, the result will be green no matter the Zone and the output on the consule will show the same instant on different formats.

2021-11-13T22:52:14.974925+01:00
2021-11-13T21:52:14.974925Z
2021-11-13T21:52:14.974925
2021-11-13T21:52:14.974925Z

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