时区
时区转换
Timezones 以 ZoneId 来区分。可以通过静态构造方法很容易的创建，Timezones 定义了 Instants 与 Local Dates 之间的转化关系：
System.out.println(ZoneId.getAvailableZoneIds());
// prints all available timezone ids
ZoneId zone1 = ZoneId.of("Europe/Berlin");
ZoneId zone2 = ZoneId.of("Brazil/East");
System.out.println(zone1.getRules());
System.out.println(zone2.getRules());
// ZoneRules[currentStandardOffset=+01:00]
// ZoneRules[currentStandardOffset=-03:00]
LocalDateTime ldt = ...
ZonedDateTime zdt = ldt.atZone(ZoneId.systemDefault());
Date output = Date.from(zdt.toInstant());
ZoneId losAngeles = ZoneId.of("America/Los_Angeles");
ZoneId berlin = ZoneId.of("Europe/Berlin");
// 2014-02-20 12:00
LocalDateTime dateTime = LocalDateTime.of(2014, 02, 20, 12, 0);
// 2014-02-20 12:00, Europe/Berlin (+01:00)
ZonedDateTime berlinDateTime = ZonedDateTime.of(dateTime, berlin);
// 2014-02-20 03:00, America/Los_Angeles (-08:00)
ZonedDateTime losAngelesDateTime = berlinDateTime.withZoneSameInstant(losAngeles);
int offsetInSeconds = losAngelesDateTime.getOffset().getTotalSeconds(); // -28800
// a collection of all available zones
Set<String> allZoneIds = ZoneId.getAvailableZoneIds();
// using offsets
LocalDateTime date = LocalDateTime.of(2013, Month.JULY, 20, 3, 30);
ZoneOffset offset = ZoneOffset.of("+05:00");
// 2013-07-20 03:30 +05:00
OffsetDateTime plusFive = OffsetDateTime.of(date, offset);
// 2013-07-19 20:30 -02:00
OffsetDateTime minusTwo = plusFive.withOffsetSameInstant(ZoneOffset.ofHours(-2));
时差
Period 类以年月日来表示日期差，而 Duration 以秒与毫秒来表示时间差；Duration 适用于处理 Instant 与机器时间。
// periods
LocalDate firstDate = LocalDate.of(2010, 5, 17); // 2010-05-17
LocalDate secondDate = LocalDate.of(2015, 3, 7); // 2015-03-07
Period period = Period.between(firstDate, secondDate);
int days = period.getDays(); // 18
int months = period.getMonths(); // 9
int years = period.getYears(); // 4
boolean isNegative = period.isNegative(); // false
Period twoMonthsAndFiveDays = Period.ofMonths(2).plusDays(5);
LocalDate sixthOfJanuary = LocalDate.of(2014, 1, 6);
// add two months and five days to 2014-01-06, result is 2014-03-11
LocalDate eleventhOfMarch = sixthOfJanuary.plus(twoMonthsAndFiveDays);
// durations
Instant firstInstant= Instant.ofEpochSecond( 1294881180 ); // 2011-01-13 01:13
Instant secondInstant = Instant.ofEpochSecond(1294708260); // 2011-01-11 01:11
Duration between = Duration.between(firstInstant, secondInstant);
// negative because firstInstant is after secondInstant (-172920)
long seconds = between.getSeconds();
// get absolute result in minutes (2882)
long absoluteResult = between.abs().toMinutes();
// two hours in seconds (7200)
long twoHoursInSeconds = Duration.ofHours(2).getSeconds();