Brand new Date and Time API

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Brand new Date and Time API March 21, 2014 HASUNUMA Kenji [email protected] http://www.coppermine.jp/ Twitter:

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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.

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What is time? “Time” is described by science approaches and deﬁned by International Standard (SI) exactly. Skip

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Deﬁnition of second (Traditional)

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Deﬁnition of second (Modern)

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PST (Paciﬁc Standard Time) Offset:-08:00 (Summer:-07:00) JST (Japan Standard Time) Offset:+09:00 Skip

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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)

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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

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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

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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)

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ISO 8601 Date elements and interchange formats - Information interchange - Representation of dates and times Skip

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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.

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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

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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)

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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

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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

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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

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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

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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

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Origin of week

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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

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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

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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

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JSR 310 Date and Time API Skip

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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/

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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

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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

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Date and Time conversions

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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”

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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

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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);

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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/ChronoZonedDateTime instead of LocalDateTime/ZonedDateTime • dates/times that have different chronology can convert by from method each other.

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

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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

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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”)

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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೥M݄d೔(E)" ฏ੒26೥3݄21೔(ۚ)

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External representation (for Human)

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Internal representation (for Machine)

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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.

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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.

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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);

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

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

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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

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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]

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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

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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

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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

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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

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// 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);

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Brand new Date and Time API March 21, 2014 HASUNUMA Kenji [email protected] http://www.coppermine.jp/ Twitter: @khasunuma