Module java.base
Package java.time.chrono

Class IsoChronology

  • All Implemented Interfaces:
    Serializable, Comparable<Chronology>, Chronology
    public final class IsoChronology
extends AbstractChronology
implements Serializable
    The ISO calendar system.

    This chronology defines the rules of the ISO calendar system. This calendar system is based on the ISO-8601 standard, which is the de facto world calendar.

    The fields are defined as follows:

    • era - There are two eras, 'Current Era' (CE) and 'Before Current Era' (BCE).
    • year-of-era - The year-of-era is the same as the proleptic-year for the current CE era. For the BCE era before the ISO epoch the year increases from 1 upwards as time goes backwards.
    • proleptic-year - The proleptic year is the same as the year-of-era for the current era. For the previous era, years have zero, then negative values.
    • month-of-year - There are 12 months in an ISO year, numbered from 1 to 12.
    • day-of-month - There are between 28 and 31 days in each of the ISO month, numbered from 1 to 31. Months 4, 6, 9 and 11 have 30 days, Months 1, 3, 5, 7, 8, 10 and 12 have 31 days. Month 2 has 28 days, or 29 in a leap year.
    • day-of-year - There are 365 days in a standard ISO year and 366 in a leap year. The days are numbered from 1 to 365 or 1 to 366.
    • leap-year - Leap years occur every 4 years, except where the year is divisble by 100 and not divisble by 400.

    Implementation Requirements:
    This class is immutable and thread-safe.
    Since:
    1.8
    See Also:
    Serialized Form

    • Field Detail

      • INSTANCE

        public static final IsoChronology INSTANCE
        Singleton instance of the ISO chronology.

    • Method Detail

      • getCalendarType

        public String getCalendarType()
        Gets the calendar type of the underlying calendar system - 'iso8601'.

        The calendar type is an identifier defined by the Unicode Locale Data Markup Language (LDML) specification. It can be used to lookup the Chronology using Chronology.of(String). It can also be used as part of a locale, accessible via Locale.getUnicodeLocaleType(String) with the key 'ca'.

        Specified by:
        getCalendarType in interface Chronology
        Returns:
        the calendar system type - 'iso8601'
        See Also:
        getId()

      • date

        public LocalDate date​(Era era,
                      int yearOfEra,
                      int month,
                      int dayOfMonth)
        Obtains an ISO local date from the era, year-of-era, month-of-year and day-of-month fields.
        Specified by:
        date in interface Chronology
        Parameters:
        era - the ISO era, not null
        yearOfEra - the ISO year-of-era
        month - the ISO month-of-year
        dayOfMonth - the ISO day-of-month
        Returns:
        the ISO local date, not null
        Throws:
        DateTimeException - if unable to create the date
        ClassCastException - if the type of era is not IsoEra

      • date

        public LocalDate date​(int prolepticYear,
                      int month,
                      int dayOfMonth)
        Obtains an ISO local date from the proleptic-year, month-of-year and day-of-month fields.

        This is equivalent to LocalDate.of(int, int, int).

        Specified by:
        date in interface Chronology
        Parameters:
        prolepticYear - the ISO proleptic-year
        month - the ISO month-of-year
        dayOfMonth - the ISO day-of-month
        Returns:
        the ISO local date, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateYearDay

        public LocalDate dateYearDay​(Era era,
                             int yearOfEra,
                             int dayOfYear)
        Obtains an ISO local date from the era, year-of-era and day-of-year fields.
        Specified by:
        dateYearDay in interface Chronology
        Parameters:
        era - the ISO era, not null
        yearOfEra - the ISO year-of-era
        dayOfYear - the ISO day-of-year
        Returns:
        the ISO local date, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateYearDay

        public LocalDate dateYearDay​(int prolepticYear,
                             int dayOfYear)
        Obtains an ISO local date from the proleptic-year and day-of-year fields.

        This is equivalent to LocalDate.ofYearDay(int, int).

        Specified by:
        dateYearDay in interface Chronology
        Parameters:
        prolepticYear - the ISO proleptic-year
        dayOfYear - the ISO day-of-year
        Returns:
        the ISO local date, not null
        Throws:
        DateTimeException - if unable to create the date

      • epochSecond

        public long epochSecond​(int prolepticYear,
                        int month,
                        int dayOfMonth,
                        int hour,
                        int minute,
                        int second,
                        ZoneOffset zoneOffset)
        Gets the number of seconds from the epoch of 1970-01-01T00:00:00Z.

        The number of seconds is calculated using the year, month, day-of-month, hour, minute, second, and zoneOffset.

        Specified by:
        epochSecond in interface Chronology
        Parameters:
        prolepticYear - the year, from MIN_YEAR to MAX_YEAR
        month - the month-of-year, from 1 to 12
        dayOfMonth - the day-of-month, from 1 to 31
        hour - the hour-of-day, from 0 to 23
        minute - the minute-of-hour, from 0 to 59
        second - the second-of-minute, from 0 to 59
        zoneOffset - the zone offset, not null
        Returns:
        the number of seconds relative to 1970-01-01T00:00:00Z, may be negative
        Throws:
        DateTimeException - if the value of any argument is out of range, or if the day-of-month is invalid for the month-of-year
        Since:
        9

      • dateNow

        public LocalDate dateNow()
        Obtains the current ISO local date from the system clock in the default time-zone.

        This will query the system clock in the default time-zone to obtain the current date.

        Using this method will prevent the ability to use an alternate clock for testing because the clock is hard-coded.

        Specified by:
        dateNow in interface Chronology
        Returns:
        the current ISO local date using the system clock and default time-zone, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateNow

        public LocalDate dateNow​(ZoneId zone)
        Obtains the current ISO local date from the system clock in the specified time-zone.

        This will query the system clock to obtain the current date. Specifying the time-zone avoids dependence on the default time-zone.

        Using this method will prevent the ability to use an alternate clock for testing because the clock is hard-coded.

        Specified by:
        dateNow in interface Chronology
        Parameters:
        zone - the zone ID to use, not null
        Returns:
        the current ISO local date using the system clock, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateNow

        public LocalDate dateNow​(Clock clock)
        Obtains the current ISO local date from the specified clock.

        This will query the specified clock to obtain the current date - today. Using this method allows the use of an alternate clock for testing. The alternate clock may be introduced using dependency injection.

        Specified by:
        dateNow in interface Chronology
        Parameters:
        clock - the clock to use, not null
        Returns:
        the current ISO local date, not null
        Throws:
        DateTimeException - if unable to create the date

      • isLeapYear

        public boolean isLeapYear​(long prolepticYear)
        Checks if the year is a leap year, according to the ISO proleptic calendar system rules.

        This method applies the current rules for leap years across the whole time-line. In general, a year is a leap year if it is divisible by four without remainder. However, years divisible by 100, are not leap years, with the exception of years divisible by 400 which are.

        For example, 1904 is a leap year it is divisible by 4. 1900 was not a leap year as it is divisible by 100, however 2000 was a leap year as it is divisible by 400.

        The calculation is proleptic - applying the same rules into the far future and far past. This is historically inaccurate, but is correct for the ISO-8601 standard.

        Specified by:
        isLeapYear in interface Chronology
        Parameters:
        prolepticYear - the ISO proleptic year to check
        Returns:
        true if the year is leap, false otherwise

      • resolveDate

        public LocalDate resolveDate​(Map<TemporalField,​Long> fieldValues,
                             ResolverStyle resolverStyle)
        Resolves parsed ChronoField values into a date during parsing.

        Most TemporalField implementations are resolved using the resolve method on the field. By contrast, the ChronoField class defines fields that only have meaning relative to the chronology. As such, ChronoField date fields are resolved here in the context of a specific chronology.

        ChronoField instances on the ISO calendar system are resolved as follows.

        • EPOCH_DAY - If present, this is converted to a LocalDate and all other date fields are then cross-checked against the date.
        • PROLEPTIC_MONTH - If present, then it is split into the YEAR and MONTH_OF_YEAR. If the mode is strict or smart then the field is validated.
        • YEAR_OF_ERA and ERA - If both are present, then they are combined to form a YEAR. In lenient mode, the YEAR_OF_ERA range is not validated, in smart and strict mode it is. The ERA is validated for range in all three modes. If only the YEAR_OF_ERA is present, and the mode is smart or lenient, then the current era (CE/AD) is assumed. In strict mode, no era is assumed and the YEAR_OF_ERA is left untouched. If only the ERA is present, then it is left untouched.
        • YEAR, MONTH_OF_YEAR and DAY_OF_MONTH - If all three are present, then they are combined to form a LocalDate. In all three modes, the YEAR is validated. If the mode is smart or strict, then the month and day are validated, with the day validated from 1 to 31. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first of January in the requested year, then adding the difference in months, then the difference in days. If the mode is smart, and the day-of-month is greater than the maximum for the year-month, then the day-of-month is adjusted to the last day-of-month. If the mode is strict, then the three fields must form a valid date.
        • YEAR and DAY_OF_YEAR - If both are present, then they are combined to form a LocalDate. In all three modes, the YEAR is validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first of January in the requested year, then adding the difference in days. If the mode is smart or strict, then the two fields must form a valid date.
        • YEAR, MONTH_OF_YEAR, ALIGNED_WEEK_OF_MONTH and ALIGNED_DAY_OF_WEEK_IN_MONTH - If all four are present, then they are combined to form a LocalDate. In all three modes, the YEAR is validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first of January in the requested year, then adding the difference in months, then the difference in weeks, then in days. If the mode is smart or strict, then the all four fields are validated to their outer ranges. The date is then combined in a manner equivalent to creating a date on the first day of the requested year and month, then adding the amount in weeks and days to reach their values. If the mode is strict, the date is additionally validated to check that the day and week adjustment did not change the month.
        • YEAR, MONTH_OF_YEAR, ALIGNED_WEEK_OF_MONTH and DAY_OF_WEEK - If all four are present, then they are combined to form a LocalDate. The approach is the same as described above for years, months and weeks in ALIGNED_DAY_OF_WEEK_IN_MONTH. The day-of-week is adjusted as the next or same matching day-of-week once the years, months and weeks have been handled.
        • YEAR, ALIGNED_WEEK_OF_YEAR and ALIGNED_DAY_OF_WEEK_IN_YEAR - If all three are present, then they are combined to form a LocalDate. In all three modes, the YEAR is validated. If the mode is lenient, then the date is combined in a manner equivalent to creating a date on the first of January in the requested year, then adding the difference in weeks, then in days. If the mode is smart or strict, then the all three fields are validated to their outer ranges. The date is then combined in a manner equivalent to creating a date on the first day of the requested year, then adding the amount in weeks and days to reach their values. If the mode is strict, the date is additionally validated to check that the day and week adjustment did not change the year.
        • YEAR, ALIGNED_WEEK_OF_YEAR and DAY_OF_WEEK - If all three are present, then they are combined to form a LocalDate. The approach is the same as described above for years and weeks in ALIGNED_DAY_OF_WEEK_IN_YEAR. The day-of-week is adjusted as the next or same matching day-of-week once the years and weeks have been handled.

        Specified by:
        resolveDate in interface Chronology
        Overrides:
        resolveDate in class AbstractChronology
        Parameters:
        fieldValues - the map of fields to values, which can be updated, not null
        resolverStyle - the requested type of resolve, not null
        Returns:
        the resolved date, null if insufficient information to create a date
        Throws:
        DateTimeException - if the date cannot be resolved, typically because of a conflict in the input data

      • period

        public Period period​(int years,
                     int months,
                     int days)
        Obtains a period for this chronology based on years, months and days.

        This returns a period tied to the ISO chronology using the specified years, months and days. See Period for further details.

        Specified by:
        period in interface Chronology
        Parameters:
        years - the number of years, may be negative
        months - the number of years, may be negative
        days - the number of years, may be negative
        Returns:
        the period in terms of this chronology, not null