我使用Java 8的新java.time实现，想知道将UTC输出到CET时间转换结果的情况。
ZonedDateTime utcTime = ZonedDateTime.of(2014, 7, 1, 8, 0, 0, 0, ZoneId.of("UTC"));
ZonedDateTime cetTime = ZonedDateTime.ofInstant(utcTime.toInstant(), ZoneId.of("CET"));
System.out.println("Summer-UTC-Time: " + utcTime);
System.out.println("Summer-CET-Time: " + cetTime);
System.out.println();
utcTime = ZonedDateTime.of(2014, 1, 1, 8, 0, 0, 0, ZoneId.of("UTC"));
cetTime = ZonedDateTime.ofInstant(utcTime.toInstant(), ZoneId.of("CET"));
System.out.println("Winter-UTC-Time: " + utcTime);
System.out.println("Winter-CET-Time: " + cetTime);
我期望CET时间始终是UTC时间的+1，但是我得到了:
Summer-UTC-Time: 2014-07-01T08:00Z[UTC]
Summer-CET-Time: 2014-07-01T10:00+02:00[CET] -> +2 **Unexpected**
Winter-UTC-Time: 2014-01-01T08:00Z[UTC]
Winter-CET-Time: 2014-01-01T09:00+01:00[CET] -> +1 Expected
因此，显然我必须处理夏令时，这是我在使用CET时所没有想到的。
java.time CET实际上是CEST吗？如果是的话，如果我需要CET，应该使用哪个区域？ 最佳答案
IANA definition of CET遵循中欧的时区规则，其中包括冬季和夏季时间。可以看到规则here，这表明“CET”基于包括夏季时间的"C-Eur"。
在java.time中，您还可以看到完整的规则集:
ZoneId zone = ZoneId.of("CET");
System.out.println(zone);
System.out.println(zone.getRules());
for (ZoneOffsetTransition trans : zone.getRules().getTransitions()) {
System.out.println(trans);
}
for (ZoneOffsetTransitionRule rule : zone.getRules().getTransitionRules()) {
System.out.println(rule);
}
打印:
CET
ZoneRules[currentStandardOffset=+01:00]
Transition[Gap at 1916-04-30T23:00+01:00 to +02:00]
Transition[Overlap at 1916-10-01T01:00+02:00 to +01:00]
Transition[Gap at 1917-04-16T02:00+01:00 to +02:00]
Transition[Overlap at 1917-09-17T03:00+02:00 to +01:00]
Transition[Gap at 1918-04-15T02:00+01:00 to +02:00]
Transition[Overlap at 1918-09-16T03:00+02:00 to +01:00]
Transition[Gap at 1940-04-01T02:00+01:00 to +02:00]
Transition[Overlap at 1942-11-02T03:00+02:00 to +01:00]
Transition[Gap at 1943-03-29T02:00+01:00 to +02:00]
Transition[Overlap at 1943-10-04T03:00+02:00 to +01:00]
Transition[Gap at 1944-04-03T02:00+01:00 to +02:00]
Transition[Overlap at 1944-10-02T03:00+02:00 to +01:00]
Transition[Gap at 1945-04-02T02:00+01:00 to +02:00]
Transition[Overlap at 1945-09-16T03:00+02:00 to +01:00]
Transition[Gap at 1977-04-03T02:00+01:00 to +02:00]
Transition[Overlap at 1977-09-25T03:00+02:00 to +01:00]
Transition[Gap at 1978-04-02T02:00+01:00 to +02:00]
Transition[Overlap at 1978-10-01T03:00+02:00 to +01:00]
Transition[Gap at 1979-04-01T02:00+01:00 to +02:00]
Transition[Overlap at 1979-09-30T03:00+02:00 to +01:00]
Transition[Gap at 1980-04-06T02:00+01:00 to +02:00]
Transition[Overlap at 1980-09-28T03:00+02:00 to +01:00]
Transition[Gap at 1981-03-29T02:00+01:00 to +02:00]
Transition[Overlap at 1981-09-27T03:00+02:00 to +01:00]
Transition[Gap at 1982-03-28T02:00+01:00 to +02:00]
Transition[Overlap at 1982-09-26T03:00+02:00 to +01:00]
Transition[Gap at 1983-03-27T02:00+01:00 to +02:00]
Transition[Overlap at 1983-09-25T03:00+02:00 to +01:00]
Transition[Gap at 1984-03-25T02:00+01:00 to +02:00]
Transition[Overlap at 1984-09-30T03:00+02:00 to +01:00]
Transition[Gap at 1985-03-31T02:00+01:00 to +02:00]
Transition[Overlap at 1985-09-29T03:00+02:00 to +01:00]
Transition[Gap at 1986-03-30T02:00+01:00 to +02:00]
Transition[Overlap at 1986-09-28T03:00+02:00 to +01:00]
Transition[Gap at 1987-03-29T02:00+01:00 to +02:00]
Transition[Overlap at 1987-09-27T03:00+02:00 to +01:00]
Transition[Gap at 1988-03-27T02:00+01:00 to +02:00]
Transition[Overlap at 1988-09-25T03:00+02:00 to +01:00]
Transition[Gap at 1989-03-26T02:00+01:00 to +02:00]
Transition[Overlap at 1989-09-24T03:00+02:00 to +01:00]
Transition[Gap at 1990-03-25T02:00+01:00 to +02:00]
Transition[Overlap at 1990-09-30T03:00+02:00 to +01:00]
Transition[Gap at 1991-03-31T02:00+01:00 to +02:00]
Transition[Overlap at 1991-09-29T03:00+02:00 to +01:00]
Transition[Gap at 1992-03-29T02:00+01:00 to +02:00]
Transition[Overlap at 1992-09-27T03:00+02:00 to +01:00]
Transition[Gap at 1993-03-28T02:00+01:00 to +02:00]
Transition[Overlap at 1993-09-26T03:00+02:00 to +01:00]
Transition[Gap at 1994-03-27T02:00+01:00 to +02:00]
Transition[Overlap at 1994-09-25T03:00+02:00 to +01:00]
Transition[Gap at 1995-03-26T02:00+01:00 to +02:00]
Transition[Overlap at 1995-09-24T03:00+02:00 to +01:00]
Transition[Gap at 1996-03-31T02:00+01:00 to +02:00]
Transition[Overlap at 1996-10-27T03:00+02:00 to +01:00]
Transition[Gap at 1997-03-30T02:00+01:00 to +02:00]
Transition[Overlap at 1997-10-26T03:00+02:00 to +01:00]
TransitionRule[Gap +01:00 to +02:00, SUNDAY on or after MARCH 25 at 02:00 STANDARD, standard offset +01:00]
TransitionRule[Overlap +02:00 to +01:00, SUNDAY on or after OCTOBER 25 at 02:00 STANDARD, standard offset +01:00]
这里的关键是要了解时区标识符和该标识符的"short name"是两个不同的元素。标识符始终固定为“CET”，但是名称在“CET”和“CEST”之间变化。