Date operations (JSR-310 Date and Time API) -------------------------------------------------------------------------------- .. only:: html .. contents:: Index :depth: 4 :local: | Overview ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | This guideline recommends the use of JSR-310 Date and Time API which offers various date and time calculations, | as against ``java.util.Date`` and ``java.util.Calendar``. .. note:: Since JSR-310 Date and Time API has been introduced from Java8, using Joda Time is recommended for the environments of versions Java8 and below. For how to use Joda Time, refer :doc:`./JodaTime`. How to use ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ | Date and Time API offers various classes depending on the application such as a class exclusively handling dates and a class exclusively handling time. | In this guideline, the focus is on ``java.time.LocalDate`` , ``java.time.LocalTime`` and ``java.time.LocalDateTime``, however, since the prefix of all the methods offered by each class is same for primary date and time operations, it should be interpreted by substituting with the appropriate class name. | Classes and methods used primarily are as given below. | | **Primary class for handling date and time** .. list-table:: :header-rows: 1 :widths: 30 35 35 * - Class name - Description - Primary factory methods * - | `java.time.LocalDate `_ | `java.time.LocalTime `_ | `java.time.LocalDateTime `_ - Class which handles date and time operation and does not possess information about timezone difference - | ``now`` Generated by current date and time | ``of`` Generated by any date and time | ``parse`` Generated from date and time string | ``from`` Generated from other objects with date and time information * - | `java.time.OffsetTime `_ | `java.time.OffsetDateTime `_ | `java.time.ZonedDateTime `_ - Class which handles date and time operation considering timezone difference - Same as above * - | `java.time.chrono.JapaneseDate `_ - Class to handle Japanese calendar operations - Same as above | | **Primary class for handling information about time period** .. list-table:: :header-rows: 1 :widths: 30 35 35 * - Class name - Description - Primary factory methods * - | `java.time.Period `_ | `java.time.Duration `_ - Class which handles date and time base, time base period - | ``between`` Generated from the difference between two objects with date and time information | ``from`` Generated from another object that contains amount of time | ``of`` Generated in any time period | | **Class for handling format** .. list-table:: :header-rows: 1 :widths: 30 35 35 * - Class name - Description - Primary factory method * - | `java.time.format.DateTimeFormatter `_ - Class which handles operations related to date and time format - | ``ofPattern`` Generates a formatter in specified pattern | | How to use each class and method is explained below. | .. note:: For the topics that are not covered in the guideline, refer `Javadoc `_ for details. .. note:: Date and Time API class is immutable (date and time calculation result is considered as a new object, and changes do not occur in the objects for calculation). Fetch date and time """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" Fetch by current date and time '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | ``java.time.LocalTime`` , ``java.time.LocalDate`` and ``java.time.LocalDateTime`` must be selectively used in accordance with the purpose for which it is to be used. Example is shown below. 1. Use ``java.time.LocalTime`` when only time is to be fetched. .. code-block:: java LocalTime localTime = LocalTime.now(); 2. Use ``java.time.LocalDate`` when only date is to be fetched. .. code-block:: java LocalDate localDate = LocalDate.now(); 3. Use ``java.time.LocalDateTime`` when both date and time are to be fetched. .. code-block:: java LocalDateTime localDateTime = LocalDateTime.now(); | Fetch by specifying year, month, day, hours, minutes and seconds '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | Specific date and time can be specified by using of method. Example is shown below. 1. Specify time and fetch ``java.time.LocalTime``. .. code-block:: java // 23:30:59 LocalTime localTime = LocalTime.of(23, 30, 59); 2. Specify date and fetch ``java.time.LocalDate``. .. code-block:: java // 2015/12/25 LocalDate localDate = LocalDate.of(2015, 12, 25); 3. Specify date and time and fetch ``java.time.LocalDateTime``. .. code-block:: java // 2015/12/25 23:30:59 LocalDateTime localDateTime = LocalDateTime.of(2015, 12, 25, 23, 30, 59); | | Also, various dates and times can be fetched by using ``java.time.temporal.TemporalAdjusters``. .. code-block:: java // LeapYear(2012/2) LocalDate localDate1 = LocalDate.of(2012, 2, 1); // Last day of month(2012/2/29) LocalDate localDate2 = localDate1.with(TemporalAdjusters.lastDayOfMonth()); // Next monday（2012/2/6） LocalDate localDate3 = localDate1.with(TemporalAdjusters.next(DayOfWeek.MONDAY)); .. note:: Unlike the specifications of ``java.util.Calendar``, calendar month starts from 1. Fetch date and time when time zone is specified '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | When an international application is to be created, a design must be adopted considering the time zone. | ``java.time.OffsetTime`` , ``java.time.OffsetDateTime`` and ``java.time.ZonedDateTime`` must be used selectively in Date and Time API in accordance with the purpose for which it is to be used. | Example is given below. 1. Use ``java.time.OffsetTime`` when the time difference between time + UTC is to be fetched. .. code-block:: java // Ex, 12:30:11.567+09:00 OffsetTime offsetTime = OffsetTime.now(); 2. Use ``java.time.OffsetDateTime`` when the time difference between date, time + UTC is to be fetched. .. code-block:: java // Ex, 2015-12-25T12:30:11.567+09:00 OffsetDateTime offsetDateTime = OffsetDateTime.now(); 3. Use ``java.time.ZonedDateTime`` when the time difference and region for date, time + UTC is to be fetched. .. code-block:: java // Ex, 2015-12-25T12:30:11.567+09:00[Asia/Tokyo] ZonedDateTime zonedDateTime = ZonedDateTime.now(); | Further, current date and time considering the time zone can be fetched in all these methods by specifying ``java.time.ZoneId`` which indicates time zone in the argument. | ``java.time.ZoneId`` example is shown below. .. code-block:: java ZoneId zoneIdTokyo = ZoneId.of("Asia/Tokyo"); OffsetTime offsetTime = OffsetTime.now(zoneIdTokyo); | Note that, ``java.time.ZoneId`` consists of a method to be defined by region name/area name format and a method defined by time difference from UTC. .. code-block:: java ZoneId.of("Asia/Tokyo"); ZoneId.of("UTC+01:00"); | | Although purpose of using ``java.time.OffsetDateTime`` and ``java.time.ZonedDateTime`` is similar, the basic difference is as given below. | An appropriate class should be selected according to the characteristics of the system to be created. .. list-table:: :header-rows: 1 :widths: 50 50 * - Class name - Description * - | ``java.time.OffsetDateTime`` - Since it only consists of quantitative value (only time difference), system does not undergo any change even if there is a change in the concept of time for each area. * - | ``java.time.ZonedDateTime`` - Since it includes concept of region besides time difference, the system undergoes change when a change occurs in the concept of time for each region.(when daylight saving etc is included as a policy) Time period """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" Fetch time period '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | ``java.time.Period`` is used while handling date based period and ``java.time.Duration`` is used while handling time based period. | Since day represented by ``java.time.Duration`` is of exactly 24 hours, expected results may not be obtained if daylight saving changes are not incorporated. | On the contrary, since ``java.time.Period`` represents 1 day including daylight saving, an error does not occur even in the system which handles daylight saving. | Example is given below. .. code-block:: java LocalDate date1 = LocalDate.of(2010, 01, 15); LocalDate date2 = LocalDate.of(2011, 03, 18); LocalTime time1 = LocalTime.of(11, 50, 50); LocalTime time2 = LocalTime.of(12, 52, 53); // One year, two months and three days. Period pd = Period.between(date1, date2); // One hour, two minutes and three seconds. Duration dn = Duration.between(time1, time2); | .. note:: A method can also be employed wherein the period is generated by specifying it by using ``of`` method. For details, refer `Javadoc of Period, Duration `_. Type conversion """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" Interoperability of each class of Date and Time API '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | ``java.time.LocalTime`` , ``java.time.LocalDate`` and ``java.time.LocalDateTime`` can easily be mutually converted. Example is given below. 1. Conversion from ``java.time.LocalTime`` to ``java.time.LocalDateTime``. .. code-block:: java // Ex. 12:10:30 LocalTime localTime = LocalTime.now(); // 2015-12-25 12:10:30 LocalDateTime localDateTime = localTime.atDate(LocalDate.of(2015, 12, 25)); 2. Conversion from ``java.time.LocalDate`` to ``java.time.LocalDateTime``. .. code-block:: java // Ex. 2012-12-25 LocalDate localDate = LocalDate.now(); // 2015-12-25 12:10:30 LocalDateTime localDateTime = localDate.atTime(LocalTime.of(12, 10, 30)); 3. Conversion from ``java.time.LocalDateTime`` to ``java.time.LocalTime`` and ``java.time.LocalDate``. .. code-block:: java // Ex. 2015-12-25 12:10:30 LocalDateTime localDateTime = LocalDateTime.now(); // 12:10:30 LocalTime localTime = localDateTime.toLocalTime(); // 2012-12-25 LocalDate localDate = localDateTime.toLocalDate(); | | Similarly, ``java.time.OffsetTime`` , ``java.time.OffsetDateTime`` and ``java.time.ZonedDateTime`` can also be easily mutually converted. Example is given below. 1. Conversion from ``java.time.OffsetTime`` to ``java.time.OffsetDateTime``. .. code-block:: java // Ex, 12:30:11.567+09:00 OffsetTime offsetTime = OffsetTime.now(); // 2015-12-25T12:30:11.567+09:00 OffsetDateTime offsetDateTime = offsetTime.atDate(LocalDate.of(2015, 12, 25)); 2. Conversion from ``java.time.OffsetDateTime`` to ``java.time.ZonedDateTime``. .. code-block:: java // Ex, 2015-12-25T12:30:11.567+09:00 OffsetDateTime offsetDateTime = OffsetDateTime.now(); // 2015-12-25T12:30:11.567+09:00[Asia/Tokyo] ZonedDateTime zonedDateTime = offsetDateTime.atZoneSameInstant(ZoneId.of("Asia/Tokyo")); 3. Conversion from ``java.time.ZonedDateTime`` to ``java.time.OffsetDateTime`` and ``java.time.OffsetTime``. .. code-block:: java // Ex, 2015-12-25T12:30:11.567+09:00[Asia/Tokyo] ZonedDateTime zonedDateTime = ZonedDateTime.now(); // 2015-12-25T12:30:11.567+09:00 OffsetDateTime offsetDateTime = zonedDateTime.toOffsetDateTime(); // 12:30:11.567+09:00 OffsetTime offsetTime = zonedDateTime.toOffsetDateTime().toOffsetTime(); | | Also, ``java.time.LocalTime`` can be converted to ``java.time.OffsetTime`` by adding time difference information. .. code-block:: java // Ex, 12:30:11.567 LocalTime localTime = LocalTime.now(); // 12:30:11.567+09:00 OffsetTime offsetTime = localTime.atOffset(ZoneOffset.ofHours(9)); | | Besides, conversion to another class is also possible by adding missing information (date information is not adequate in case of conversion from ``LocalTime`` to ``LocalDateTime``). | Conversion method begins with the prefix ``at`` or ``to``. For details, refer `Javadoc of each class `_ . Interoperability with java.util.Date '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' A method which directly converts ``java.time.LocalDate`` class to ``java.util.Date`` is not provided. | However, since a method which converts ``java.time.Instant`` offered by Date and Time API is added to ``java.util.Date`` from Java8 and subsequent versions, a conversion can be carried out through ``java.time.Instant``. | Example is given below. 1. Conversion from ``java.time.LocalDateTime`` to ``java.util.Date``. .. code-block:: java LocalDateTime localDateTime = LocalDateTime.now(); Instant instant = localDateTime.toInstant(ZoneOffset.ofHours(9)); Date date = Date.from(instant); 2. Conversion from ``java.util.Date`` to ``java.time.LocalDateTime``. .. code-block:: java Date date = new Date(); Instant instant = date.toInstant(); LocalDateTime localDateTime = LocalDateTime.ofInstant(instant, ZoneId.systemDefault()); | .. note:: Since ``java.time.LocalTime`` and ``java.time.LocalDate`` do not contain Instant values, it is necessary to convert once to ``java.time.LocalDateTime``. Interoperability with java.sqlpackage '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | An upgrade is added to ``java.sql`` package from Java8 version and a method for mutual conversion with ``java.time`` package is defined. | Example is given below. 1. Conversion from ``java.sql.Date`` to ``java.time.LocalDate``. .. code-block:: java java.sql.Date date = new java.sql.Date(System.currentTimeMillis()); LocalDate localDate = date.toLocalDate(); 2. Conversion from ``java.time.LocalDate`` to ``java.sql.Date``. .. code-block:: java LocalDate localDate = LocalDate.now(); java.sql.Date date = java.sql.Date.valueOf(localDate); 3. Conversion from ``java.sql.Time`` to ``java.time.LocalTime``. .. code-block:: java java.sql.Time time = new java.sql.Time(System.currentTimeMillis()); LocalTime localTime = time.toLocalTime(); 4. Conversion from ``java.time.LocalTime`` to ``java.sql.Time``. .. code-block:: java LocalTime localTime = LocalTime.now(); java.sql.Time time = java.sql.Time.valueOf(localTime); 5. Conversion from ``java.sql.Timestamp`` to ``java.time.LocalDateTime``. .. code-block:: java java.sql.Timestamp timestamp = new java.sql.Timestamp(System.currentTimeMillis()); LocalDateTime localDateTime = timestamp.toLocalDateTime(); 6. Conversion from ``java.time.LocalDateTime`` to ``java.sql.Timestamp``. .. code-block:: java LocalDateTime localDateTime = LocalDateTime.now(); java.sql.Timestamp timestamp = java.sql.Timestamp.valueOf(localDateTime); How to use org.terasoluna.gfw.common.date package '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | Currently, Date Factory for Date and Time API is not provided in the common library. (Refer: :doc:`SystemDate`) | However, ``java.time.LocalDate`` can be generated by using ``org.terasoluna.gfw.common.date.ClassicDateFactory`` and ``java.sql.Date`` as an interim measure. | It can be generated by converting from ``java.time.LocalDate`` even for the ``java.time.LocalTime`` and ``java.time.LocalDateTime`` classes. | Example is given below. **bean definition file ([projectname]-env.xml)** .. code-block:: xml **Java class** .. code-block:: java @Inject ClassicDateFactory dateFactory; public DateFactorySample getSystemDate() { java.sql.Date date = dateFactory.newSqlDate(); LocalDate localDate = date.toLocalDate(); // omitted } | .. note:: Date Factory corresponding to Date and Time API will be added later. Format for the string '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | A method which uses ``toString`` method and a method which uses ``java.time.fomat.DateTimeFormatter`` can be used for converting the object containing date and time information to string. | When outputting any date and time string, conversion to various date and time strings can be done by using ``java.time.fomat.DateTimeFormatter``. | | ``java.time.fomat.DateTimeFormatter`` consists of a method which uses a formatter of predefined ISO pattern and a method which is used by defining a format of any pattern. .. code-block:: java DateTimeFormatter formatter1 = DateTimeFormatter.BASIC_ISO_DATE; DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("G uuuu/MM/dd E") .withLocale(Locale.JAPANESE) .withResolverStyle(ResolverStyle.STRICT); | At that time, ``Locale`` and ``ResolverStyle`` (strict) can be defined besides string format. | Since default value of ``Locale`` changes depending on the system, it should be set at the time of initialization. | Also, when ``ResolverStyle`` (strict) uses ``ofPattern`` method, ``ResolverStyle.SMART`` is set as default, however, in this guideline, it is recommended to specify ``ResolverStyle.STRICT`` for strict interpretation of date to avoid occurrence of unexpected behaviour.（When ISO pattern formatter is to be used, ``ResolverStyle.STRICT`` is specified.) | | Also, since format ``yyyy`` in Date and Time API represent year in the calendar, interpretation will be different according to the calendar. (Year will be 2015 according to Western calendar but will be 0027 according to Japanese calendar). | When western calendar is to be indicated, it is recommended to use ``uuuu`` format instead of ``yyyy`` format.For the defined format list, refer `DateTimeFormatter `_ . | | Example is given below. .. code-block:: java DateTimeFormatter formatter1 = DateTimeFormatter.BASIC_ISO_DATE; DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("G uuuu/MM/dd E") .withLocale(Locale.JAPANESE) .withResolverStyle(ResolverStyle.STRICT); LocalDate localDate1 = LocalDate.of(2015, 12, 25); // "2015-12-25" System.out.println(localDate1.toString()); // "20151225" System.out.println(formatter1.format(localDate1)); // "Western calendar 2015/12/25 Friday" System.out.println(formatter2.format(localDate1)); | | Also, when the strings are to be displayed on the screen, | dedicated JSP tags do not exist in Date and Time API unlike Joda Time. | Since ``fmt:formatDate`` tag of JSTL handles only ``java.util.Date`` and ``java.util.TimeZone`` objects, | formatted string is passed and displayed when the date and time information held by object of Date and Time API on JSP is to be displayed. **Controller class** .. code-block:: java @Controller public class HomeController { @RequestMapping(value = "/", method = {RequestMethod.GET, RequestMethod.POST}) public String home(Model model, Locale locale) { DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("uuuu/MM/dd") .withLocale(locale) .withResolverStyle(ResolverStyle.STRICT); LocalDate localDate1 = LocalDate.now(); model.addAttribute("currentDate", localDate1.toString()); model.addAttribute("formattedCurrentDateString", dateFormatter.format(localDate1)); // omitted } } **jsp file** .. code-block:: jsp

currentDate = ${f:h(currentDate)}.

formattedCurrentDateString = ${f:h(formattedCurrentDateString)}.

**Output results example (html)** .. code-block:: html

currentDate = 2015-12-25.

formattedCurrentDateString = 2015/12/25.

Path from the string '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | Similar to conversion to string, various date strings can be converted to Date and Time API class by using ``java.time.fomat.DateTimeFormatter``. | Example is as shown below. .. code-block:: java DateTimeFormatter formatter1 = DateTimeFormatter.ofPattern("uuuu/MM/dd") .withLocale(Locale.JAPANESE) .withResolverStyle(ResolverStyle.STRICT); DateTimeFormatter formatter2 = DateTimeFormatter.ofPattern("HH:mm:ss") .withLocale(Locale.JAPANESE) .withResolverStyle(ResolverStyle.STRICT); LocalDate localDate = LocalDate.parse("2015/12/25", formatter1); LocalTime localTime = LocalDate.parse("14:09:20", formatter2); | Date operation """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" | Date and time can be easily calculated and compared in Date and Time API. | Example is as shown below. Date and time calculation '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | ``plus`` method and ``minus`` method are provided for calculating date and time. 1. Example for calculating time. .. code-block:: java LocalTime localTime = LocalTime.of(20, 30, 50); LocalTime plusHoursTime = localTime.plusHours(2); LocalTime plusMinutesTime = localTime.plusMinutes(10); LocalTime minusSecondsTime = localTime.minusSeconds(15); 2. Example for calculating date. .. code-block:: java LocalDate localDate = LocalDate.of(2015, 12, 25); LocalDate plusYearsDate = localDate.plusYears(10); LocalDate minusMonthsTime = localDate.minusMonths(1); LocalDate plusDaysTime = localDate.plusDays(3); | .. note:: If a negative number is passed in the ``plus`` method, results similar to the results at the time of using ``minus`` method can be obtained. Same for ``minus`` method. Date and time comparison '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | Time series for past, future and current period can be compared in Date and Time API. | Example is as shown below. 1. Example for comparison of time. .. code-block:: java LocalTime morning = LocalTime.of(7, 30, 00); LocalTime daytime = LocalTime.of(12, 00, 00); LocalTime evening = LocalTime.of(17, 30, 00); daytime.isBefore(morning); // false morning.isAfter(evening); // true evening.equals(LocalTime.of(17, 30, 00)); // true daytime.isBefore(daytime); // false morning.isAfter(morning); // false 2. Example for comparison of date. .. code-block:: java LocalDate may = LocalDate.of(2015, 6, 1); LocalDate june = LocalDate.of(2015, 7, 1); LocalDate july = LocalDate.of(2015, 8, 1); may.isBefore(june); // true june.isAfter(july); // false july.equals(may); // false may.isBefore(may); // false june.isAfter(june); // false | | Note that, the class applicable to ``Interval`` of Joda Time currently does not exist in Date and Time API. Determination of date and time '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | Example for determining date and time is shown below. 1. When a valid date and time string is to be determined, it can be determined based on the occurrence and non-occurrence of ``java.time.format.DateTimeParseException``. .. code-block:: java String strDateTime = "aabbcc"; DateTimeFormatter timeFormatter = DateTimeFormatter.ofPattern("HHmmss") .withLocale(Locale.JAPANESE) .withResolverStyle(ResolverStyle.STRICT);; DateTimeFormatter dateFormatter = DateTimeFormatter.ofPattern("uuMMdd") .withLocale(Locale.JAPANESE) .withResolverStyle(ResolverStyle.STRICT);; try { // DateTimeParseException LocalTime localTime = LocalTime.parse(strDateTime, timeFormatter); } catch (DateTimeParseException e) { System.out.println("Invalid time string !!"); } try { // DateTimeParseException LocalDate localDate = LocalDate.parse(strDateTime, dateFormatter); } catch (DateTimeParseException e) { System.out.println("Invalid date string !!"); } 2. When a leap year is to be determined, ``isLeapYear`` method of ``java.time.LocalDate`` can be used. .. code-block:: java LocalDate date1 = LocalDate.of(2012, 1, 1); LocalDate date2 = LocalDate.of(2015, 1, 1); date1.isLeapYear(); // true date2.isLeapYear(); // false Fetching year, month, day, hours, minutes, seconds '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | When the respective year, month, day, hours, minutes and seconds are to be fetched, use ``get`` method. | An example to fetch information related to date is shown below. .. code-block:: java LocalDate localDate = LocalDate.of(2015, 2, 1); // 2015 int year = localDate.getYear(); // 2 int month = localDate.getMonthValue(); // 1 int dayOfMonth = localDate.getDayOfMonth(); // 32 ( day of year ) int dayOfYear = localDate.getDayOfYear(); Japanese calendar （JapaneseDate） """""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""" | A class called ``java.time.chrono.JapaneseDate`` is provided in Date and Time API to handle Japanese calendar. .. note:: ``java.time.chrono.JapaneseDate`` cannot be used before Meiji 6 (1873 of Western calendar) when the Gregorian calendar was introduced. Fetching Japanese calendar '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | Similar to ``java.time.LocalDate``, Japanese calendar can be fetched by using ``now`` method and ``of`` method. | Further, Japanese calendar can also be fetched by using ``java.time.chrono.JapaneseEra`` class. | Example is shown below. .. code-block:: java JapaneseDate japaneseDate1 = JapaneseDate.now(); JapaneseDate japaneseDate2 = JapaneseDate.of(2015, 12, 25); JapaneseDate japaneseDate3 = JapaneseDate.of(JapaneseEra.HEISEI, 27, 12, 25); | An exception occurs when a value prior to Meiji 6 is specified in the argument. .. code-block:: java // DateTimeException JapaneseDate japaneseDate = JapaneseDate.of(1500, 1, 1); Format for the string '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | It is possible to convert to Japanese calendar date by using ``java.time.fomat.DateTimeFormatter``. While using, calendar is set to ``java.time.chrono.JapaneseChronology`` by using ``DateTimeFormatter#withChronology`` method. | Since various formats can be handled in Japanese calendar dates as well, output can be obtained corresponding to the requirements like zero-filling or space-filling etc. | An example wherein Japanese calendar is displayed using space filling is shown below. .. code-block:: java DateTimeFormatter formatter = DateTimeFormatter.ofPattern("GppyYearppMMonthppdDay") .withLocale(Locale.JAPANESE) .withResolverStyle(ResolverStyle.STRICT) .withChronology(JapaneseChronology.INSTANCE); JapaneseDate japaneseDate = JapaneseDate.of(1992, 1, 1); // "Heisei YY4 MM1 DD1" System.out.println(formatter.format(japaneseDate)); Path from the string '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | Japanese string can be converted to ``java.time.chrono.JapaneseDate`` by using ``java.time.fomat.DateTimeFormatter``. | Example is shown below. .. code-block:: java DateTimeFormatter formatter = DateTimeFormatter.ofPattern("GyYearMMMonthddDate") .withLocale(Locale.JAPANESE) .withResolverStyle(ResolverStyle.STRICT) .withChronology(JapaneseChronology.INSTANCE); JapaneseDate japaneseDate1 = JapaneseDate.from(formatter.parse("Heisei 27YY12MM25DD")); JapaneseDate japaneseDate2 = JapaneseDate.from(formatter.parse("Meiji YY6MM01DD01")); Conversion of Western and Japanese calendar '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''' | Conversion between Western and Japanese calendars can be easily carried out from ``java.time.LocalDate`` by using from method. .. code-block:: java LocalDate localDate = LocalDate.of(2015, 12, 25); JapaneseDate jpDate = JapaneseDate.from(localDate);