Daylight Saving Time
The Java time API uses the tz
database to handle DST rules for
each time zone. While the typical use case is to convert instants to local
times the API also allows to query the database and e.g. list all DST
transitions for a specific time zone.
Since Java 8
import java.time.Instant;
import java.time.LocalDate;
import java.time.ZoneId;
import java.time.zone.ZoneOffsetTransition;
import java.time.zone.ZoneRules;
public class DaylightSavingTime {
public static void main(String... args) {
ZoneId zone = ZoneId.of("Europe/Zurich");
Instant from = LocalDate.of(2020, 1, 1).atStartOfDay().atZone(zone).toInstant();
Instant to = LocalDate.of(2030, 1, 1).atStartOfDay().atZone(zone).toInstant();
System.out.printf("DST transitions in %s between %s and %s:\n", zone, from, to);
ZoneRules rules = zone.getRules();
ZoneOffsetTransition t = rules.nextTransition(from);
while (t.getInstant().isBefore(to)) {
System.out.println(t);
t = rules.nextTransition(t.getInstant());
}
}
}
This snippet at GitHub
