WithZoneSameInstant

WithZoneSameInstant is a method in the Java time API used to convert a ZonedDateTime to the same moment in a different time zone. It is defined on the ZonedDateTime class (java.time.ZonedDateTime) and takes a ZoneId as its parameter.

The method returns a new ZonedDateTime that represents the same instant in time as the original, but with the specified zone. In the result, the offset from UTC may change, and the local date-time fields (year, month, day, hour, minute, second) will be adjusted according to the rules of the new zone. If the supplied zone is the same as the current zone, the result is effectively identical to the original instance.

The signature is public ZonedDateTime withZoneSameInstant(ZoneId zone). If zone is null, a NullPointerException is thrown. The method preserves the instant across zones, unlike withZoneSameLocal, which preserves the local date-time fields and can change the instant.

This method is often used when displaying a moment to users in different time zones or when converting timestamps for cross-zone storage or display while keeping the underlying moment unchanged. Because ZonedDateTime is immutable, withZoneSameInstant returns a new instance rather than modifying the original.

In summary, withZoneSameInstant provides a straightforward way to re-express a specific moment in time in another time zone, ensuring the moment’s truth is preserved while the calendar fields reflect the target zone.