How to ask a java.time.ZonedDateTime
object if Daylight Saving Time (DST) applies to its moment or if standard time applies?
@Jon's answer is good. Just want to mention there is ZoneRules#isDaylightSavings available.
ZonedDateTime zdt = ...;
ZoneRules rules = zdt.getZone().getRules();
boolean isDst = rules.isDaylightSavings(zdt.toInstant());
And possible duplicate question here.