This document provides an overview of the Java 8 Date and Time API as defined by JSR 310. It describes the key classes like Instant, LocalDate, LocalDateTime, and ZonedDateTime and how they can be used to work with dates, times, durations, and timezones. Examples are given showing how to get the current date and time, parse and format dates, add/subtract periods, and convert between different date and time representations.

1. JSR 310
Date and Time API
©2015 Ady
-- everything about date and time in Java 8

2. JSR 310
https://jcp.org/en/jsr/detail?id=310

3. Classes
Class/Enum Y M D H m s Z toString()
Instant √ 2014-12-16T09:42:57.054Z
LocalDate √ √ √ 2014-12-16
LocateDateTime √ √ √ √ √ √ 2014-12-16T17:42:57.196
ZonedDateTime √ √ √ √ √ √ √ 2014-12-16T17:42:57.197+08:00[Asia/Chongqing]
LocalTime √ √ √ 17:42:57.197
MonthDay √ √ --12-16
Year √ 2014
YearMonth √ √ 2014-12
Month √ DECEMBER
OffsetDateTime √ √ √ √ √ √ √ 2014-12-16T17:42:57.231+08:00
OffsetTime √ √ √ √ 17:42:57.232+08:00
Duration √ PT3H
Period √ √ √ P2014Y12M31D

4. LocalDate today = LocalDate.now();

5. LocalDate today = LocalDate.now();
int year = today.getYear();
int month = today.getMonthValue();
int day = today.getDayOfMonth();

6. LocalDate dayOfBirth = LocalDate.of(2015,10,14);

7. LocalDate date1 = LocalDate.of(2015,10,14);
if( date1.equals(today) ){
}

8. MonthDay birthday = MonthDay.of(12,4);

9. LocalTime = LocalTime.now();

10. LocalDateTime now = LocalDateTime.now();
System.out.println(now); //2015-10-14T11:23:50.083

11. LocalTime now = LocalTime.now();
LocalTime oneHour = now.plusHours(1);

12. LocalDate now = LocalDate.now();
System.out.println(now);
LocalDate nextMonth = now.plus(1, ChronoUnit.MONTHS);
System.out.println(nextMonth);

13. LocalDate now = LocalDate.now();
LocalDate next = LocalDate.of(2015,10,14);
boolean r = now.isBefore(next);
boolean r2 = now.isAfter(next);

14. YearMonth ym = YearMonth.of(2016, Month.FEBRUARY);
System.out.println(ym.isLeapYear()); // true
System.out.println(ym.lengthOfMonth()); // 29
System.out.println(ym.lengthOfYear()); // 366
.

15. LocalDate today = LocalDate.now();
LocalDate birthday = LocalDate.of(2012,10,15);
Period p = Period.between(birthday, today);
System.out.println(p); // P2Y11M29D

16. LocalDate birthday = LocalDate.of(2012, 10, 15);
LocalDate today = LocalDate.now();
System.out.println(ChronoUnit.DAYS.between(birthday, today)); //1094
System.out.println(ChronoUnit.MONTHS.between(birthday, today)); //35

17. LocalDateTime now = LocalDateTime.now();
LocalDateTime birthDay = LocalDateTime.of(2012,10,15,9,30);
Duration d = Duration.between(birthDay,now);
System.out.println(d); //PT26258H17M34.68S
System.out.println(d.toDays()); //1094

18. ZonedDateTime now = ZonedDateTime.now();
ZoneId parisZoneId = ZoneId.of("Europe/Paris");
ZonedDateTime parisNow = now.withZoneSameInstant(parisZoneId);
System.out.println("Beijing: " + now); //Beijing: 2015-10-14T10:46:23.397+08:00[Asia/Shanghai]
System.out.println("Paris: " + parisNow);//Paris: 2015-10-14T04:46:23.397+02:00[Europe/Paris]

19. Instant now = Instant.now();
System.out.println(now.toString()); // 2015-10-14T03:18:52.324Z
System.out.println(now.toEpochMilli()); // 1444792732324
System.out.println(now.getEpochSecond()); // 1444792732

20. System.out.println(Clock.systemUTC().millis()); // 1444792912772
System.out.println(Clock.systemDefaultZone().millis()); // 1444792912772
System.out.println(System.currentTimeMillis()); //1444792912772

21. LocalDateTime now = LocalDateTime.now();
System.out.println(now); //2015-10-14T11:23:50.083
DateTimeFormatter format = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
System.out.println(now.format(format)); //2015-10-14 11:23:50

22. DateTimeFormatter format = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
LocalDateTime dtime = LocalDateTime.parse("2015-10-14 11:23:50", format);

23. Main Method
now static factory instance of now LocalDateTime.now()
of static factory create instance LocalDate.of(2014,12,16)
from static factory convert input to target YearMonth.from(localDate)
parse static factory parse string to target YearMonth.parse("2014-12")
format instance format instance to string LocalDate.format(DateTimeFormatter.ISO_DATE)
get instance get a part LocalDate.get(ChronoField.DAY_OF_YEAR)
is instance compare with LocalDate.isBefore/isAfter/isEqual
with instance return copy with changed LocalDate.with(ChronoField.YEAR,2016)
plus instance return copy with added LocalDate.plusYears(1)
minus instance return copy with subtracted LocalDateTime.minusMonths(1)
to instance convert instance to target LocalDateTime.toLocalTime()
at instance combine two instance LocalDate.atTime(12,30,0)

24. Date now = new Date();
Instant ins = now.toInstant();
Date oldDate = new Date(ins.toEpochMilli());
Date oldDate2 = Date.from(ins);
Instant ins2 = LocalDateTime.now().toInstant(ZoneOffset.UTC);
Timestamp t = Timestamp.valueOf(LocalDateTime.now());
Instant ins3 = t.toInstant();
Instant

25. 1

26. 2
/Instants 1444792732324
/Periods P2Y11M29D
/Dates 2015-10-14
/Times 11:42:45
/Timezones +08:00/Asia/Shanghai
/Durations PT26258H17M34.68S
https://zh.wikipedia.org/wiki/ISO_8601

27. 3
Instant
LocalDate
LocalTime
LocalDateTime
ZonedDateTime

28. 4
ZoneId
ChronoUnit
DateTimeFormatter
Duration
Period
OffsetDateTime

29. The End

30. https://github.com/adyliu
http://www.slideshare.net/xylz/