Easiest way to calculate offset between two timezones Scala/Java

Question

I din't find good answer how to easy calculate timezone offset for given point of time in Scala/Java.

Given:

• date with time
• timezone 1
• timezone 2

Requirements: calculate offset for particular date in timezone 1, required to move this date to timezone 2.

Example:

datetime = 2017-10-23 00:00:00 in America/Los_Angeles timezone 1,

timezone 2 = Europe/Paris

Offset should equal +9, it can be used to move date from timezone 1 to timezone 2.

Answer 1

Wouldn't this do it?

import java.time.{LocalDateTime, ZoneId}
import java.time.temporal.ChronoUnit

val dateOfInterest = LocalDateTime.parse("2020-02-02T12:00")

ChronoUnit.HOURS.between(dateOfInterest.atZone(ZoneId.of("Europe/Paris"))
                        ,dateOfInterest.atZone(ZoneId.of("America/Los_Angeles")))
//res0: Long = 9