Brand New Date and Time API (2014-03-21)

1. Brand new
Date and Time API
March 21, 2014
HASUNUMA Kenji
khasunuma@java.net
http://www.coppermine.jp/
Twitter:

2. Preface
• JSR 310 is a new and improved date and time API
for Java.
• It is based on ISO 8601 standard.
• The reference implementation is called "ThreeTen".
• Specification Leads: Stephen Colebourne, Michael
Nascimento Santos and Roger Riggs.

3. What is time?
“Time” is described by science approaches and defined by
International Standard (SI) exactly.
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5. Definition of second (Traditional)

6. Definition of second (Modern)

10. PST (Pacific Standard Time)
Offset:-08:00 (Summer:-07:00)
JST (Japan Standard Time)
Offset:+09:00
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11. Time zones (East 1/2)
Code Name Offset Summer
ECT Europe/Paris +01:00 +02:00
CAT Africa/Harare +02:00 (N/A)
ART Africa/Cairo +02:00 (N/A)
EAT Africa/Addis_Abeba +03:00 (N/A)
NET Asia/Yerevan +04:00 (N/A)
PLT Asia/Karachi +05:00 (N/A)
IST Asia/Koltaka +05:30 (N/A)
BST Asia/Dacca +06:00 (N/A)

12. Time zones (East 2/2)
Code Name Offset Summer
VST Asia/Ho_Chi_Minh +07:00 (N/A)
CTT Asia/Shanghai +08:00 (N/A)
JST Asia/Tokyo +09:00 (N/A)
ACT Australia/Darwin +09:30 (N/A)
AET Australia/Sydney +11:00 +10:00
SST Pacific/Guadalcanal +11:00 (N/A)
NST Pacific/Auckland +13:00 +12:00
MIT Pacific/Apia +14:00 +13:00

13. Time zones (West 1/2)
Code Name Offset Summer
BET America/Sao_Paulo -02:00 -03:00
AGT America/Argentina/Buenos_Aires -03:00 (N/A)
CNT America/St_Johns -03:30 -02:30
PRT America/Puerto_Rico -04:00 (N/A)
EST (N/A) -05:00 (N/A)
IET America/Indiana/Indianapolis -05:00 -04:00

14. Time zones (West 2/2)
Code Name Offset Summer
CST America/Chicago -06:00 -05:00
MST (N/A) -07:00 (N/A)
PNT America/Phoenix -07:00 (N/A)
PST America/Los_Angeles -08:00 -07:00
AST America/Anchorage -09:00 -08:00
HST (N/A) -10:00 (N/A)

15. ISO 8601
Date elements and interchange formats - Information
interchange - Representation of dates and times
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16. What’s ISO 8601?
• International standard for representation of dates
and times, using information interchange.
• Based on Gregorian calendar system (1582).
• JIS X 0301 is Japanese translations with remarks
about Japanese chronology.
• ISO 8601 and Unix time are incompatible.
Unix time is basis of java.util.Date, et al.

17. Representation of time
(w/o Time zone)
• hh:mm:ss e.g. 15:30:45
• hh:mm e.g. 15:30
• hh e.g. 15
• hh:mm:ss.s e.g. 15:30:45.250

18. Representation of time
(w/Time zone)
• Add suffix based on the offset from UTC
• UTC: ‘Z’ e.g. 06:30:45Z
• Not UTC: +hh:mm or -hh:mm
e.g. 15:30:45+09:00 (JST, Asia/Tokyo)
02:30:45-08:00 (PST, America/Los_Angeles)

19. Representation of date
• date - it consists with year, month, day and week.
• calendar date YYYY-MM-DD e.g. 2014-03-21
• ordinal date YYYY-DDD e.g. 2014-080
• week date YYYY-Www-D e.g. 2014-W12-5
• Short representations:
• year-month YYYY-MM e.g. 2014-03
• year YYYY e.g. 2014
• century YY e.g. 20
• month-day --MM-DD e.g. --03-21

20. Definition of day
• a day = 24 hours = 86,400 seconds
• 00:00~24:00 (24:00 is same as next 00:00)
• Exceptions:
• Leap seconds
• Begin and end of summer time
• When the time zone is changed

21. Definition of month
• a month = 28, 29, 30 or 31 days
1 January 01~31 7 July 01~31
2 February 01~28/29 8 August 01~31
3 March 01~31 9 September 01~30
4 April 01~30 10 October 01~31
5 May 01~31 11 November 01~30
6 June 01~30 12 December 01~31

22. Definition of year
• a year = approximation days while the orbital period
of Earth (365.242 19 days), 12 months.
• common year = 365 days
• leap year = 366 days
• 0000~9999 (0000~1582 is reserved)
mod 4 mod 100 mod 400 year
Not Zero - - common year
Zero Not Zero - leap year
Zero Zero Not Zero common year
Zero Zero Zero leap year

23. Definition of week
• a week = 7 days
• 1st week of year = a week
contents the first Thursday
of the year.
• a year contents 52 or 53
weeks.
1 Monday
2 Tuesday
3 Wednesday
4 Thursday
5 Friday
6 Saturday
7 Sunday

24. Origin of week

25. Representation of date and time
• concat date and time by 'T'.
• YYYY-MM-DDThh:mm:ss[Time zone]
• Alt. YYYY-DDDThh:mm:ss[Time Zone]
• e.g.
2014-03-21T06:30
2014-03-21T15:30:45+09:00
2014-079T02:30:45-08:00

26. Definition and representation
of duration
• time amount between two time points
• date : nYnMnD e.g. 1Y3M22D
• time : nHnMnS e.g. 9H30M45S
• date and time : nYnMnDTnHnMnS
e.g. 1Y3M22DT9H30M45S

27. Definition and representation
of period
• range between two dates (adopt also two times)
• two dates : YYYY-MM-DD/YYYY-MM-DD
e.g. 2013-12-31/2014-03-21
• start date and duration : YYYY-MM-DD/PnYnMnD
e.g. 2013-12-31/P1Y3M22D
• end date and duration : PnYnMnD/YYYY-MM-DD
e.g. P1Y3M22D/2013-03-21
• duration : PnYnMnD
e.g. P1Y3M22D

28. JSR 310
Date and Time API
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29. JSR 310 : Date and Time API
• Since 2007, Reference Implementation: ThreeTen
• Relational projects:
• ThreeTen-Extra: Features dropped from JDK8,
i.e. UTC/TAI full support, Coptic chronology, et al.
https://github.com/ThreeTen/threeten-extra
• ThreeTen-Backport: JSR 310 like API for JDK7.
https://github.com/ThreeTen/threetenbp
• Joda-Time: Provides many hints to JSR 310.
http://www.joda.org/joda-time/

30. Package java.time.*
Package Description Use
java.time Basic classes usually
java.time.format Date and Time Formatter often
java.time.chrono Chronology supports partially
java.time.temporal Low-level API rarely
java.time.zone Low-level API rarely

31. Date and Time classes
Class Field Time zone ISO 8601 Chrono.
LocalDate Date N/A compatible enable
LocalDateTime Date + Time N/A compatible enable
LocalTime Time N/A compatible N/A
OffsetDateTime Date + Time offset compatible disable
OffsetTime Time offset compatible N/A
ZonedDateTime Date + Time zone id extended enable

32. Date and Time conversions

33. Date and Time conversions
Oper. Description
of-
Create from fields.
e.g. LocalDate today = LocalDate.of(2014, 3, 21);
// today.toString() : “2014-03-21”
at-
Expand with fields.
e.g. LocalDateTime current = today.atTime(15:30);
// current.toString() : “2014-03-21T15:30:00”
to-
Truncate fields.
e.g. LocalDate someday = current.toLocalDate();
// someday.toString() : “2014-03-21”

34. Date and Time operators
Oper. Description
isBefore
isEqual
isAfter
Compare with other date/time.
e.g. LocalDate today = LocalDate.of(2014, 3, 21);
boolean b = today.isAfter(LocalDate.of(2014, 3, 19));
// b == true
plus-
minus-
Add/subtract field value.
e.g. LocalDate tomorrow = today.plusDays(2);
// tomorrow.toString() : “2014-03-23”
isLeapYear
Verify a date is leap year.
e.g. boolean leap = today.isLeapYear();
// leap == false

35. Date and Time formatting
Method Description
toString()
Format using default formatter.
e.g. String s = today.toString();
// s : “2014-03-21”
format(DateTimeFormatter f)
Format using custom formatter.
e.g. String s = today.format(formatter);
parse(String s)
Parse using default formatter.
e.g. LocalDate d = LocalDate
.parse(“2014-03-21”);
parse(String s,
DateTimeFormatter f)
Parse using custom formatter.
e.g. LocalDate d = LocalDate
.parse(“2014-03-21”, formatter);

36. Chronology
• Date and Time API supports ISO 8601 and some local
chronology (e.g., Japanese Era, Minguo Era, Thai
Buddhist Era and Hijrah Era).
• ChronoLocalDate and its sub-classes (incl. LocalDate)
support chronology.
• ChronoLocalDateTime<D>/ChronoZonedDateTime<D>
instead of LocalDateTime/ZonedDateTime
• dates/times that have different chronology can convert
by from method each other.

37. Chronology supports
Chronology Era ChronoLocalDate
IsoChronology IsoEra LocalDate
JapaneseChronology JapaneseEra JapaneseDate
MinguoChronology MinguoEra MinguoDate
ThaiBuddhistChronology ThaiBuddhistEra ThaiBuddhistDate
HijrahChronology HijrahEra HijrahDate

38. Chronology examples
LocalDate today = LocalDate.of(2014, 3, 21);
System.out.println(today);
System.out.println(JapaneseDate.from(today));
System.out.println(MinguoDate.from(today));
System.out.println(ThaiBuddhistDate.from(today));
System.out.println(HijrahDate.from(today));
2014-03-21
Japanese Heisei 26-03-21
Minguo ROC 103-03-21
ThaiBuddhist BE 2557-03-21
Hijrah-umalqura AH 1435-05-20

39. DateTimeFormatter
• Provides formats date/time.
• Created by ofPattern method (basic way)
e.g. DateTimeFormatter.ofPattern(“yyyy/MM/dd”)
• Created by DateTimeFormatterBuilder (full control)
• Pre-defined patterns (static fields)
• ISO_LOCAL_DATE // ofPattern(“yyyy-MM-dd”)
• ISO_ORDINAL_DATE // ofPattern(“yyyy-ddd”)
• ISO_WEEK_DATE // ofPattern(“yyyy-Www”)

40. Chronology and Formatter
e.g. JapaneseDate
pattern display example
"YYYY/MM/dd" 2014/03/21
"Y/M/d" 2014/3/21
"GGGGGyy.MM.dd" H26.03.21
"Gy年M月d日(E)" 平成26年3月21日(金)

41. External representation
(for Human)

42. Internal representation
(for Machine)

43. Instant
• Representation of a time-point.
• The precision is a nano second.
• The epoch is 1970-01-01T00:00:00Z
• Convert from/to LocalDateTime, OffsetDateTime or
ZonedDateTime.
• Convert from/to java.util.Date, which means that
Instant is the only interface to java.util.Date.

44. Duration and Period
• Representations of period (ISO 8601).
• Period (JSR 310) is a period (ISO 8601) between two
dates and represents as a date-scale.
i.e. format as "P1Y2M3D"
• Duration (JSR 310) is a period (ISO 8601) between
any two temporals and represents as a time-scale.
i.e. format as "PT15H30M45D"
• Attention: those definitions are different from them of
ISO 8601.

45. Clock and now method
• Provider of the current instant.
• There are some clocks, having relation of zones (incl.
current zone), fixed clock (for testing) and custom.
• By default, it uses the clock of current zone.
• now method (LocalDate, et al.) creates a temporal
instance from a clock.
e.g. LocalDate.now();
LocalDate.now(zoneId);
LocalDate.now(Clock.fixed(instant, ZoneId.systemDefault);

46. Examples
More examples:
https://github.com/btnrouge/threetensamples
Skip

47. // It is assumed to run at March 21, 2014
LocalDate today = LocalDate.new();
!
System.out.println(today);
2014-03-21

48. LocalDate calendarDate
= LocalDate.of(2014, 3, 21);
LocalDate ordinalDate
= LocalDate.ofYearDays(2014, 80);
LocalDateTime localDateTime
= LocalDateTime.of(2014, 3, 21, 15, 30);
!
System.out.println(calendarDate);
System.out.println(ordinalDate);
System.out.println(localDateTime);
2014-03-21
2014-03-21
2014-03-21T15:30

49. OffsetDateTime offsetDateTime
= OffsetDateTime.of(2014, 3, 21,
15, 30, 45, 0,
ZoneOffset.ofHours(9));
ZonedDateTime zonedDateTime
= ZonedDateTime.of(2014, 3, 21,
15, 30, 45, 0,
ZoneId.of("Asia/Tokyo"));
!
System.out.println(offsetDateTime);
System.out.println(zonedDateTime);
2014-03-21T15:30:45+09:00
2014-03-21T15:30:45+09:00[Asia/Tokyo]

50. LocalDate localDate
= LocalDate.of(2014, 3, 21);
LocalDateTime localDateTime0
= localDate.atStartOfDay();
LocalDateTime localDateTime1
= localDate.atTime(15, 30, 45);
OffsetDateTime offsetDateTime
= localDateTime.atOffset(
ZoneOffset.ofHours(9));
!
System.out.println(localDateTime0);
System.out.println(localDateTime1);
System.out.println(offsetDateTime);
2014-03-21T00:00
2014-03-21T15:30:45
2014-03-21T15:30:45+09:00

51. OffsetDateTime offsetDateTime
= OffsetDateTime.of(2014, 3, 21,
15, 30, 45, 0,
ZoneOffset.ofHours(9));
LocalDate localDate =
offsetDateTime.toLocalDate();
LocalTime localTime =
offsetDateTime.toLocalTime();
!
System.out.println(offsetDateTime);
System.out.println(localDate);
System.out.println(localTime);
2014-03-21T15:30:45+09:00
2014-03-21
15:30:45

52. LocalDate commonYearsDay
= LocalDate.of(1990, 12, 19);
LocalDate leapYearsDay
= LocalDate.of(1992, 10, 8);
LocalDate centuryDay
= LocalDate.of(2000, 1, 1);
!
System.out.println(
commonYearDay.isLeapYear());
System.out.println(
leapYearDay.isLeap());
System.out.println(
centuryDay.isLeapYear());
false
true
false

53. LocalDate today
= LocalDate.of(2014, 3, 21);
LocalDate lastWeek
= today.minusWeeks(1L);
LocalDate dayAfterTomorrow
= today.plusDays(2L);
Period period =
lastWeek.until(dayAfterTomorrow);
!
System.out.println(yesterday);
System.out.println(dayAftereTomorrow);
System.out.println(period);
2014-03-20
2014-03-23
P9D

54. // Convert java.util.Date to LocalDateTime
Date date = new Date();
!
LocalDateTime localDateTime =
LocalDateTime.ofInstant(date.toInstant(),
ZoneId.systemDefault());
// Convert LocalDateTime to java.util.Date
LocalDateTime localDateTime =
LocalDateTime.now();
!
Instant instant = localDateTime.atZone(
ZoneId.systemDefault()).toInstant();
Date date = Date.from(instant);

55. Brand new
Date and Time API
March 21, 2014
HASUNUMA Kenji
khasunuma@java.net
http://www.coppermine.jp/
Twitter: @khasunuma