How to convert a time to another time zone

Short answer

Attach the time to a zone with atZone(), then withZoneSameInstant() shows the same moment in another zone:

void main() {
    var berlin = LocalDateTime.of(2026, 3, 8, 15, 0).atZone(ZoneId.of("Europe/Berlin"));
    var tokyo = berlin.withZoneSameInstant(ZoneId.of("Asia/Tokyo"));
 
    IO.println(berlin);
    IO.println(tokyo);
}

Output:

2026-03-08T15:00+01:00[Europe/Berlin]
2026-03-08T23:00+09:00[Asia/Tokyo]

From UTC

Server time is often stored as an Instant in UTC. Show it to the user in their zone:

void main() {
    Instant stored = Instant.parse("2026-07-01T12:00:00Z");
    var local = stored.atZone(ZoneId.of("America/New_York"));
 
    IO.println(local.toLocalDateTime());
}

Output:

2026-07-01T08:00

Daylight saving time

ZoneId knows about daylight saving changes. The same time of day on different dates gives a different offset:

void main() {
    var zone = ZoneId.of("Europe/London");
 
    IO.println(LocalDateTime.of(2026, 1, 15, 12, 0).atZone(zone).getOffset());
    IO.println(LocalDateTime.of(2026, 7, 15, 12, 0).atZone(zone).getOffset());
}

Output:

Z
+01:00

Z means a zero offset from UTC: in winter London is on UTC, and in summer it is an hour ahead.

Common mistake

Using withZoneSameLocal() instead of withZoneSameInstant(). It keeps the clock time and only changes the zone — that is a different moment:

void main() {
    var berlin = LocalDateTime.of(2026, 3, 8, 15, 0).atZone(ZoneId.of("Europe/Berlin"));
 
    IO.println(berlin.withZoneSameLocal(ZoneId.of("Asia/Tokyo")));
    IO.println(berlin.withZoneSameInstant(ZoneId.of("Asia/Tokyo")));
}

Output:

2026-03-08T15:00+09:00[Asia/Tokyo]
2026-03-08T23:00+09:00[Asia/Tokyo]

Thanks for reading!

Short answer

From UTC

Daylight saving time

Common mistake

Functions used in this recipe

Thanks for reading!