IsoChronology

AI-generated Key Takeaways

• IsoChronology represents the ISO-8601 calendar system, the international standard for date and time representation.

• It provides methods for creating LocalDate instances using various inputs like year, month, day, era, and dayOfYear.

• IsoChronology handles leap years according to the standard ISO-8601 rules (every 4 years, except for years divisible by 100 but not by 400).

• It offers functionalities for retrieving the current date, determining if a year is a leap year, and creating periods.

• The class provides a singleton instance, INSTANCE, for easy access to the IsoChronology.

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.

Field Summary

public static final IsoChronology

INSTANCE

Singleton instance of the ISO chronology.

Public Method Summary

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.
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.
LocalDate	date(TemporalAccessor temporal) Obtains an ISO local date from another date-time object.
LocalDate	dateEpochDay(long epochDay) Obtains an ISO local date from the epoch-day.
LocalDate	dateNow(ZoneId zone) Obtains the current ISO local date from the system clock in the specified time-zone.
LocalDate	dateNow() Obtains the current ISO local date from the system clock in the default time-zone.
LocalDate	dateNow(Clock clock) Obtains the current ISO local date from the specified clock.
LocalDate	dateYearDay(Era era, int yearOfEra, int dayOfYear) Obtains an ISO local date from the era, year-of-era and day-of-year fields.
LocalDate	dateYearDay(int prolepticYear, int dayOfYear) Obtains an ISO local date from the proleptic-year and day-of-year fields.
IsoEra	eraOf(int eraValue)
List<Era>	eras()
String	getCalendarType() Gets the calendar type of the underlying calendar system - 'iso8601'.
String	getId() Gets the ID of the chronology - 'ISO'.
boolean	isLeapYear(long prolepticYear) Checks if the year is a leap year, according to the ISO proleptic calendar system rules.
LocalDateTime	localDateTime(TemporalAccessor temporal) Obtains an ISO local date-time from another date-time object.
Period	period(int years, int months, int days) Obtains a period for this chronology based on years, months and days.
int	prolepticYear(Era era, int yearOfEra)
ValueRange	range(ChronoField field)
LocalDate	resolveDate(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) Resolves parsed ChronoField values into a date during parsing.
ZonedDateTime	zonedDateTime(TemporalAccessor temporal) Obtains an ISO zoned date-time from another date-time object.
ZonedDateTime	zonedDateTime(Instant instant, ZoneId zone) Obtains an ISO zoned date-time in this chronology from an Instant.

Inherited Method Summary

From class java.time.chrono.AbstractChronology

int	compareTo(Chronology other) Compares this chronology to another chronology.
boolean	equals(Object obj) Checks if this chronology is equal to another chronology.
int	hashCode() A hash code for this chronology.
ChronoLocalDate	resolveDate(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) Resolves parsed ChronoField values into a date during parsing.
String	toString() Outputs this chronology as a String, using the chronology ID.

From class java.lang.Object

Object	clone() Creates and returns a copy of this Object.
boolean	equals(Object obj) Compares this instance with the specified object and indicates if they are equal.
void	finalize() Invoked when the garbage collector has detected that this instance is no longer reachable.
final Class<?>	getClass() Returns the unique instance of Class that represents this object's class.
int	hashCode() Returns an integer hash code for this object.
final void	notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
final void	notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up.
String	toString() Returns a string containing a concise, human-readable description of this object.
final void	wait(long timeout, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait(long timeout) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
final void	wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object.

From interface java.time.chrono.Chronology

abstract int	compareTo(Chronology other) Compares this chronology to another chronology.
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.
abstract 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.
abstract ChronoLocalDate	date(TemporalAccessor temporal) Obtains a local date in this chronology from another temporal object.
abstract ChronoLocalDate	dateEpochDay(long epochDay) Obtains a local date in this chronology from the epoch-day.
ChronoLocalDate	dateNow(Clock clock) Obtains the current local date in this chronology from the specified clock.
ChronoLocalDate	dateNow(ZoneId zone) Obtains the current local date in this chronology from the system clock in the specified time-zone.
ChronoLocalDate	dateNow() Obtains the current local date in this chronology from the system clock in the default time-zone.
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.
abstract ChronoLocalDate	dateYearDay(int prolepticYear, int dayOfYear) Obtains a local date in this chronology from the proleptic-year and day-of-year fields.
abstract boolean	equals(Object obj) Checks if this chronology is equal to another chronology.
abstract Era	eraOf(int eraValue) Creates the chronology era object from the numeric value.
abstract List<Era>	eras() Gets the list of eras for the chronology.
static Chronology	from(TemporalAccessor temporal) Obtains an instance of Chronology from a temporal object.
static Set<Chronology>	getAvailableChronologies() Returns the available chronologies.
abstract String	getCalendarType() Gets the calendar type of the calendar system.
String	getDisplayName(TextStyle style, Locale locale) Gets the textual representation of this chronology.
abstract String	getId() Gets the ID of the chronology.
abstract int	hashCode() A hash code for this chronology.
abstract boolean	isLeapYear(long prolepticYear) Checks if the specified year is a leap year.
ChronoLocalDateTime<? extends ChronoLocalDate>	localDateTime(TemporalAccessor temporal) Obtains a local date-time in this chronology from another temporal object.
static Chronology	of(String id) Obtains an instance of Chronology from a chronology ID or calendar system type.
static Chronology	ofLocale(Locale locale) Obtains an instance of Chronology from a locale.
ChronoPeriod	period(int years, int months, int days) Obtains a period for this chronology based on years, months and days.
abstract int	prolepticYear(Era era, int yearOfEra) Calculates the proleptic-year given the era and year-of-era.
abstract ValueRange	range(ChronoField field) Gets the range of valid values for the specified field.
abstract ChronoLocalDate	resolveDate(Map<TemporalField, Long> fieldValues, ResolverStyle resolverStyle) Resolves parsed ChronoField values into a date during parsing.
abstract String	toString() Outputs this chronology as a String.
ChronoZonedDateTime<? extends ChronoLocalDate>	zonedDateTime(Instant instant, ZoneId zone) Obtains a ChronoZonedDateTime in this chronology from an Instant.
ChronoZonedDateTime<? extends ChronoLocalDate>	zonedDateTime(TemporalAccessor temporal) Obtains a ChronoZonedDateTime in this chronology from another temporal object.

From interface java.lang.Comparable

abstract int

compareTo(Chronology o) Compares this object with the specified object for order.

Fields

public static final IsoChronology INSTANCE

Singleton instance of the ISO chronology.

Public Methods

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).

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

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.

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

public LocalDate date (TemporalAccessor temporal)

Obtains an ISO local date from another date-time object.

This is equivalent to LocalDate.from(TemporalAccessor).

Parameters

temporal	the date-time object to convert, not null

Returns

• the ISO local date, not null

Throws

DateTimeException	if unable to create the date

public LocalDate dateEpochDay (long epochDay)

Obtains an ISO local date from the epoch-day.

This is equivalent to LocalDate.ofEpochDay(long).

Parameters

epochDay	the epoch day

Returns

• the ISO local date, not null

Throws

DateTimeException	if unable to create the date

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.

Parameters

zone

Returns

• the current ISO local date using the system clock, not null

Throws

DateTimeException	if unable to create the date

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.

Returns

• the current ISO local date using the system clock and default time-zone, not null

Throws

DateTimeException	if unable to create the date

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.

Parameters

clock	the clock to use, not null

Returns

• the current ISO local date, not null

Throws

DateTimeException	if unable to create the date

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.

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

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).

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

public IsoEra eraOf (int eraValue)

Parameters

eraValue

public List<Era> eras ()

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'.

Returns

• the calendar system type - 'iso8601'

See Also

• getId()

public String getId ()

Gets the ID of the chronology - 'ISO'.

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

Returns

• the chronology ID - 'ISO'

See Also

• getCalendarType()

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.

Parameters

prolepticYear	the ISO proleptic year to check

Returns

• true if the year is leap, false otherwise

public LocalDateTime localDateTime (TemporalAccessor temporal)

Obtains an ISO local date-time from another date-time object.

This is equivalent to LocalDateTime.from(TemporalAccessor).

Parameters

temporal	the date-time object to convert, not null

Returns

• the ISO local date-time, not null

Throws

DateTimeException	if unable to create the date-time

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.

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 nullthe ISO period, not null

public int prolepticYear (Era era, int yearOfEra)

Parameters

era
yearOfEra

public ValueRange range (ChronoField field)

Parameters

field

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.

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

public ZonedDateTime zonedDateTime (TemporalAccessor temporal)

Obtains an ISO zoned date-time from another date-time object.

This is equivalent to ZonedDateTime.from(TemporalAccessor).

Parameters

temporal	the date-time object to convert, not null

Returns

• the ISO zoned date-time, not null

Throws

DateTimeException	if unable to create the date-time

public ZonedDateTime zonedDateTime (Instant instant, ZoneId zone)

Obtains an ISO zoned date-time in this chronology from an Instant.

This is equivalent to ZonedDateTime.ofInstant(Instant, ZoneId).

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