How can I convert Java ZonedDateTime to OffsetDateTime with default time zone offset?

Question

Say I have a ZonedDateTime of 2018-10-30T18:04:58.874Z : How can I convert this to OffsetDateTime 2018-10-30T13:04:58.874-05:00

I'd prefer the offset to be the default/system offset, for example pulled from OffsetDateTime.now().

Lita

What methods of ZonedDateTime do you think can be useful here? – Massage

Answer 1

From your ZonedDateTime you need to specify in which other zone you want your OffsetDateTime, precise the zone and them use .toOffsetDateTime() :

ZonedDateTime z = ZonedDateTime.parse("2018-10-30T18:04:58.874Z");
System.out.println(z); //2018-10-30T18:04:58.874Z

OffsetDateTime o = z.withZoneSameInstant(ZoneId.of("UTC-5")).toOffsetDateTime();
System.out.println(o); //2018-10-30T13:04:58.874-05:00

Collinsia

Answer 2

This will shift the time zone from current/now:

someOffsetDateTime.withOffsetSameInstant(OffsetDateTime.now().getOffset())

Lita

This in general seems wrong to me: the offset can change if DST takes place and now() and tha actual date under parse can require different offsets – Middlesworth

Answer 3

I think the correct way to do it is as follows:

ZonedDateTime date = ZonedDateTime.parse("2018-10-30T18:04:58.874Z");
ZoneOffset offset = ZoneId.systemDefault().getRules().getOffset(date.toInstant());
ZonedDateTime dateInMyZone = date.withZoneSameInstant(offset)

getting it from now() will give you a possibly wrong result casue the offset can change during the year due to DST

Middlesworth