Package java.time.chrono

Interface Chronology

  • All Superinterfaces:
    java.lang.Comparable<Chronology>
    All Known Implementing Classes:
    AbstractChronology, IsoChronology
    public interface Chronology
extends java.lang.Comparable<Chronology>
    A calendar system, used to organize and identify dates.

    The main date and time API is built on the ISO calendar system. The chronology operates behind the scenes to represent the general concept of a calendar system. For example, the Japanese, Minguo, Thai Buddhist and others.

    Most other calendar systems also operate on the shared concepts of year, month and day, linked to the cycles of the Earth around the Sun, and the Moon around the Earth. These shared concepts are defined by ChronoField and are available for use by any Chronology implementation: 

       LocalDate isoDate = ...
   ThaiBuddhistDate thaiDate = ...
   int isoYear = isoDate.get(ChronoField.YEAR);
   int thaiYear = thaiDate.get(ChronoField.YEAR);
    As shown, although the date objects are in different calendar systems, represented by different Chronology instances, both can be queried using the same constant on ChronoField. For a full discussion of the implications of this, see ChronoLocalDate. In general, the advice is to use the known ISO-based LocalDate, rather than ChronoLocalDate.

    While a Chronology object typically uses ChronoField and is based on an era, year-of-era, month-of-year, day-of-month model of a date, this is not required. A Chronology instance may represent a totally different kind of calendar system, such as the Mayan.

    In practical terms, the Chronology instance also acts as a factory. The AbstractChronology.of(String) method allows an instance to be looked up by identifier.

    The Chronology instance provides a set of methods to create ChronoLocalDate instances. The date classes are used to manipulate specific dates.

    Adding New Calendars

    The set of available chronologies can be extended by applications. Adding a new calendar system requires the writing of an implementation of Chronology, ChronoLocalDate and Era. The majority of the logic specific to the calendar system will be in the ChronoLocalDate implementation. The Chronology implementation acts as a factory.

    Each chronology must define a chronology ID that is unique within the system. If the chronology represents a calendar system defined by the CLDR specification then the calendar type is the concatenation of the CLDR type and, if applicable, the CLDR variant,

    This interface must be implemented with care to ensure other classes operate correctly. All implementations that can be instantiated must be final, immutable and thread-safe. Subclasses should be Serializable wherever possible.

    • Method Detail

      • getId

        java.lang.String getId()
        Gets the ID of the chronology.

        The ID uniquely identifies the Chronology. It can be used to lookup the Chronology using AbstractChronology.of(String).

        Returns:
        the chronology ID, not null
        See Also:
        getCalendarType()

      • getCalendarType

        @Nullable
java.lang.String getCalendarType()
        Gets the calendar type of the calendar system.

        The calendar type is an identifier defined by the CLDR and Unicode Locale Data Markup Language (LDML) specifications to uniquely identification a calendar. The getCalendarType is the concatenation of the CLDR calendar type and the variant, if applicable, is appended separated by "-". The calendar type is used to lookup the Chronology using AbstractChronology.of(String).

        Returns:
        the calendar system type, null if the calendar is not defined by CLDR/LDML
        See Also:
        getId()

      • date

        ChronoLocalDate date​(Era era,
                     int yearOfEra,
                     int month,
                     int dayOfMonth)
        Obtains a local date in this chronology from the era, year-of-era, month-of-year and day-of-month fields.

        The default implementation combines the era and year-of-era into a proleptic year before calling date(int, int, int).

        Parameters:
        era - the era of the correct type for the chronology, not null
        yearOfEra - the chronology year-of-era
        month - the chronology month-of-year
        dayOfMonth - the chronology day-of-month
        Returns:
        the local date in this chronology, not null
        Throws:
        DateTimeException - if unable to create the date
        java.lang.ClassCastException - if the era is not of the correct type for the chronology

      • date

        ChronoLocalDate date​(int prolepticYear,
                     int month,
                     int dayOfMonth)
        Obtains a local date in this chronology from the proleptic-year, month-of-year and day-of-month fields.
        Parameters:
        prolepticYear - the chronology proleptic-year
        month - the chronology month-of-year
        dayOfMonth - the chronology day-of-month
        Returns:
        the local date in this chronology, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateYearDay

        ChronoLocalDate dateYearDay​(Era era,
                            int yearOfEra,
                            int dayOfYear)
        Obtains a local date in this chronology from the era, year-of-era and day-of-year fields.

        The default implementation combines the era and year-of-era into a proleptic year before calling dateYearDay(int, int).

        Parameters:
        era - the era of the correct type for the chronology, not null
        yearOfEra - the chronology year-of-era
        dayOfYear - the chronology day-of-year
        Returns:
        the local date in this chronology, not null
        Throws:
        DateTimeException - if unable to create the date
        java.lang.ClassCastException - if the era is not of the correct type for the chronology

      • dateYearDay

        ChronoLocalDate dateYearDay​(int prolepticYear,
                            int dayOfYear)
        Obtains a local date in this chronology from the proleptic-year and day-of-year fields.
        Parameters:
        prolepticYear - the chronology proleptic-year
        dayOfYear - the chronology day-of-year
        Returns:
        the local date in this chronology, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateEpochDay

        ChronoLocalDate dateEpochDay​(long epochDay)
        Obtains a local date in this chronology from the epoch-day.

        The definition of EPOCH_DAY is the same for all calendar systems, thus it can be used for conversion.

        Parameters:
        epochDay - the epoch day
        Returns:
        the local date in this chronology, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateNow

        ChronoLocalDate dateNow()
        Obtains the current local date in this chronology 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.

        The default implementation invokes dateNow(Clock).

        Returns:
        the current local date using the system clock and default time-zone, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateNow

        ChronoLocalDate dateNow​(ZoneId zone)
        Obtains the current local date in this chronology 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.

        The default implementation invokes dateNow(Clock).

        Parameters:
        zone - the zone ID to use, not null
        Returns:
        the current local date using the system clock, not null
        Throws:
        DateTimeException - if unable to create the date

      • dateNow

        ChronoLocalDate dateNow​(Clock clock)
        Obtains the current local date in this chronology 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.

        The default implementation invokes date(TemporalAccessor).

        Parameters:
        clock - the clock to use, not null
        Returns:
        the current local date, not null
        Throws:
        DateTimeException - if unable to create the date

      • date

        ChronoLocalDate date​(TemporalAccessor temporal)
        Obtains a local date in this chronology from another temporal object.

        This obtains a date in this chronology based on the specified temporal. A TemporalAccessor represents an arbitrary set of date and time information, which this factory converts to an instance of ChronoLocalDate.

        The conversion typically uses the EPOCH_DAY field, which is standardized across calendar systems.

        This method matches the signature of the functional interface TemporalQuery allowing it to be used as a query via method reference, aChronology::date.

        Parameters:
        temporal - the temporal object to convert, not null
        Returns:
        the local date in this chronology, not null
        Throws:
        DateTimeException - if unable to create the date

      • localDateTime

        ChronoLocalDateTime<? extends ChronoLocalDate> localDateTime​(TemporalAccessor temporal)
        Obtains a local date-time in this chronology from another temporal object.

        This obtains a date-time in this chronology based on the specified temporal. A TemporalAccessor represents an arbitrary set of date and time information, which this factory converts to an instance of ChronoLocalDateTime.

        The conversion extracts and combines the ChronoLocalDate and the LocalTime from the temporal object. Implementations are permitted to perform optimizations such as accessing those fields that are equivalent to the relevant objects. The result uses this chronology.

        This method matches the signature of the functional interface TemporalQuery allowing it to be used as a query via method reference, aChronology::localDateTime.

        Parameters:
        temporal - the temporal object to convert, not null
        Returns:
        the local date-time in this chronology, not null
        Throws:
        DateTimeException - if unable to create the date-time

      • zonedDateTime

        ChronoZonedDateTime<? extends ChronoLocalDate> zonedDateTime​(TemporalAccessor temporal)
        Obtains a ChronoZonedDateTime in this chronology from another temporal object.

        This obtains a zoned date-time in this chronology based on the specified temporal. A TemporalAccessor represents an arbitrary set of date and time information, which this factory converts to an instance of ChronoZonedDateTime.

        The conversion will first obtain a ZoneId from the temporal object, falling back to a ZoneOffset if necessary. It will then try to obtain an Instant, falling back to a ChronoLocalDateTime if necessary. The result will be either the combination of ZoneId or ZoneOffset with Instant or ChronoLocalDateTime. Implementations are permitted to perform optimizations such as accessing those fields that are equivalent to the relevant objects. The result uses this chronology.

        This method matches the signature of the functional interface TemporalQuery allowing it to be used as a query via method reference, aChronology::zonedDateTime.

        Parameters:
        temporal - the temporal object to convert, not null
        Returns:
        the zoned date-time in this chronology, not null
        Throws:
        DateTimeException - if unable to create the date-time

      • zonedDateTime

        ChronoZonedDateTime<? extends ChronoLocalDate> zonedDateTime​(Instant instant,
                                                             ZoneId zone)
        Obtains a ChronoZonedDateTime in this chronology from an Instant.

        This obtains a zoned date-time with the same instant as that specified.

        Parameters:
        instant - the instant to create the date-time from, not null
        zone - the time-zone, not null
        Returns:
        the zoned date-time, not null
        Throws:
        DateTimeException - if the result exceeds the supported range

      • isLeapYear

        boolean isLeapYear​(long prolepticYear)
        Checks if the specified year is a leap year.

        A leap-year is a year of a longer length than normal. The exact meaning is determined by the chronology according to the following constraints.

        • a leap-year must imply a year-length longer than a non leap-year.
        • a chronology that does not support the concept of a year must return false.
        Parameters:
        prolepticYear - the proleptic-year to check, not validated for range
        Returns:
        true if the year is a leap year

      • prolepticYear

        int prolepticYear​(Era era,
                  int yearOfEra)
        Calculates the proleptic-year given the era and year-of-era.

        This combines the era and year-of-era into the single proleptic-year field.

        If the chronology makes active use of eras, such as JapaneseChronology then the year-of-era will be validated against the era. For other chronologies, validation is optional.

        Parameters:
        era - the era of the correct type for the chronology, not null
        yearOfEra - the chronology year-of-era
        Returns:
        the proleptic-year
        Throws:
        DateTimeException - if unable to convert to a proleptic-year, such as if the year is invalid for the era
        java.lang.ClassCastException - if the era is not of the correct type for the chronology

      • eraOf

        Era eraOf​(int eraValue)
        Creates the chronology era object from the numeric value.

        The era is, conceptually, the largest division of the time-line. Most calendar systems have a single epoch dividing the time-line into two eras. However, some have multiple eras, such as one for the reign of each leader. The exact meaning is determined by the chronology according to the following constraints.

        The era in use at 1970-01-01 must have the value 1. Later eras must have sequentially higher values. Earlier eras must have sequentially lower values. Each chronology must refer to an enum or similar singleton to provide the era values.

        This method returns the singleton era of the correct type for the specified era value.

        Parameters:
        eraValue - the era value
        Returns:
        the calendar system era, not null
        Throws:
        DateTimeException - if unable to create the era

      • eras

        java.util.List<Era> eras()
        Gets the list of eras for the chronology.

        Most calendar systems have an era, within which the year has meaning. If the calendar system does not support the concept of eras, an empty list must be returned.

        Returns:
        the list of eras for the chronology, may be immutable, not null

      • range

        ValueRange range​(ChronoField field)
        Gets the range of valid values for the specified field.

        All fields can be expressed as a long integer. This method returns an object that describes the valid range for that value.

        Note that the result only describes the minimum and maximum valid values and it is important not to read too much into them. For example, there could be values within the range that are invalid for the field.

        This method will return a result whether or not the chronology supports the field.

        Parameters:
        field - the field to get the range for, not null
        Returns:
        the range of valid values for the field, not null
        Throws:
        DateTimeException - if the range for the field cannot be obtained

      • resolveDate

        @Nullable
ChronoLocalDate resolveDate​(java.util.Map<TemporalField,​java.lang.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.

        The default implementation, which explains typical resolve behaviour, is provided in 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

        ChronoPeriod 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 this chronology using the specified years, months and days. All supplied chronologies use periods based on years, months and days, however the ChronoPeriod API allows the period to be represented using other units.

        The default implementation returns an implementation class suitable for most calendar systems. It is based solely on the three units. Normalization, addition and subtraction derive the number of months in a year from the range(ChronoField). If the number of months within a year is fixed, then the calculation approach for addition, subtraction and normalization is slightly different.

        If implementing an unusual calendar system that is not based on years, months and days, or where you want direct control, then the ChronoPeriod interface must be directly implemented.

        The returned period is immutable and thread-safe.

        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

      • compareTo

        int compareTo​(Chronology other)
        Compares this chronology to another chronology.

        The comparison order first by the chronology ID string, then by any additional information specific to the subclass. It is "consistent with equals", as defined by Comparable.

        Specified by:
        compareTo in interface java.lang.Comparable<Chronology>
        Parameters:
        other - the other chronology to compare to, not null
        Returns:
        the comparator value, negative if less, positive if greater

      • equals

        boolean equals​(@Nullable
               java.lang.Object obj)
        Checks if this chronology is equal to another chronology.

        The comparison is based on the entire state of the object.

        Overrides:
        equals in class java.lang.Object
        Parameters:
        obj - the object to check, null returns false
        Returns:
        true if this is equal to the other chronology

      • hashCode

        int hashCode()
        A hash code for this chronology.

        The hash code should be based on the entire state of the object.

        Overrides:
        hashCode in class java.lang.Object
        Returns:
        a suitable hash code

      • toString

        java.lang.String toString()
        Outputs this chronology as a String.

        The format should include the entire state of the object.

        Overrides:
        toString in class java.lang.Object
        Returns:
        a string representation of this chronology, not null