Class CalendarSystem

A calendar system maps the non-calendar-specific "local time line" to human concepts such as years, months and days.

Since 1.0.x

Availability net6.0, netstandard2.0

Inheritance

object

CalendarSystem

Inherited Members

object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

Namespace: NodaTime

Assembly: NodaTime.dll

Syntax

public sealed class CalendarSystem

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

Properties

Badi

Returns the Badíʿ (meaning "wondrous" or "unique") calendar, as described at https://en.wikipedia.org/wiki/Badi_calendar. This is a purely solar calendar with years starting at the vernal equinox.

Since 2.3.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem Badi { get; }

Property Value

Type	Description
CalendarSystem	The Badíʿ calendar system.

Remarks

The Badíʿ calendar was developed and defined by the founders of the Bahá'í Faith in the mid to late 1800's A.D. The first year in the calendar coincides with 1844 A.D. Years are labeled "B.E." for Bahá'í Era.

A year consists of 19 months, each with 19 days. Each day starts at sunset. Years are grouped into sets of 19 "Unities" (Váḥid) and 19 Unities make up 1 "All Things" (Kull-i-Shay’).

A period of days (usually 4 or 5, called Ayyám-i-Há) occurs between the 18th and 19th months. The length of this period of intercalary days is solely determined by the date of the following vernal equinox. The vernal equinox is a momentary point in time, so the "date" of the equinox is determined by the date (beginning at sunset) in effect in Tehran, Iran at the moment of the equinox.

In this Noda Time implementation, days start at midnight and lookup tables are used to determine vernal equinox dates. Ayyám-i-Há is internally modelled as extra days added to the 18th month. As a result, a few functions will not work as expected for Ayyám-i-Há, such as EndOfMonth.

Coptic

Returns a Coptic calendar system, which defines every fourth year as leap, much like the Julian calendar. The year is broken down into 12 months, each 30 days in length. An extra period at the end of the year is either 5 or 6 days in length. In this implementation, it is considered a 13th month.

Since 1.4.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem Coptic { get; }

Property Value

Type	Description
CalendarSystem	A suitable Coptic calendar reference; the same reference may be returned by several calls as the object is immutable and thread-safe.

Remarks

Year 1 in the Coptic calendar began on August 29, 284 CE (Julian), thus Coptic years do not begin at the same time as Julian years. This calendar is not proleptic, as it does not allow dates before the first Coptic year.

This implementation defines a day as midnight to midnight exactly as per the ISO calendar. Some references indicate that a Coptic day starts at sunset on the previous ISO day, but this has not been confirmed and is not implemented.

Eras

Gets a read-only list of eras used in this calendar system.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public IList<Era> Eras { get; }

Property Value

Type	Description
IList<Era>	A read-only list of eras used in this calendar system.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

Gregorian

Returns a Gregorian calendar system.

Since 1.4.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem Gregorian { get; }

Property Value

Type	Description
CalendarSystem	A Gregorian calendar system.

Remarks

The Gregorian calendar system defines every fourth year as leap, unless the year is divisible by 100 and not by 400. This improves upon the Julian calendar leap year rule.

Although the Gregorian calendar did not exist before 1582 CE, this calendar system assumes it did, thus it is proleptic. This implementation also fixes the start of the year at January 1.

HebrewCivil

Returns a Hebrew calendar system using the civil month numbering, equivalent to the one used by the BCL HebrewCalendar.

Since 1.4.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem HebrewCivil { get; }

Property Value

Type	Description
CalendarSystem	A Hebrew calendar system using the civil month numbering, equivalent to the one used by the BCL.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

See Also

GetHebrewCalendar(HebrewMonthNumbering)

HebrewScriptural

Returns a Hebrew calendar system using the scriptural month numbering.

Since 1.4.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem HebrewScriptural { get; }

Property Value

Type	Description
CalendarSystem	A Hebrew calendar system using the scriptural month numbering.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

See Also

GetHebrewCalendar(HebrewMonthNumbering)

Id

Returns the unique identifier for this calendar system. This is provides full round-trip capability using ForId(string) to retrieve the calendar system from the identifier.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public string Id { get; }

Property Value

Type	Description
string	The unique identifier for this calendar system.

Remarks

A unique ID for a calendar is required when serializing types which include a CalendarSystem. As of 2 Nov 2012 (ISO calendar) there are no ISO or RFC standards for naming a calendar system. As such, the identifiers provided here are specific to Noda Time, and are not guaranteed to interoperate with any other date and time API.

Calendar ID	Equivalent factory method or property
ISO	Iso
Gregorian	Gregorian
Coptic	Coptic
Badi	Badi
Julian	Julian
Hijri Civil-Indian	GetIslamicCalendar(IslamicLeapYearPattern, IslamicEpoch)(IslamicLeapYearPattern.Indian, IslamicEpoch.Civil)
Hijri Civil-Base15	GetIslamicCalendar(IslamicLeapYearPattern, IslamicEpoch)(IslamicLeapYearPattern.Base15, IslamicEpoch.Civil)
Hijri Civil-Base16	GetIslamicCalendar(IslamicLeapYearPattern, IslamicEpoch)(IslamicLeapYearPattern.Base16, IslamicEpoch.Civil)
Hijri Civil-HabashAlHasib	GetIslamicCalendar(IslamicLeapYearPattern, IslamicEpoch)(IslamicLeapYearPattern.HabashAlHasib, IslamicEpoch.Civil)
Hijri Astronomical-Indian	GetIslamicCalendar(IslamicLeapYearPattern, IslamicEpoch)(IslamicLeapYearPattern.Indian, IslamicEpoch.Astronomical)
Hijri Astronomical-Base15	GetIslamicCalendar(IslamicLeapYearPattern, IslamicEpoch)(IslamicLeapYearPattern.Base15, IslamicEpoch.Astronomical)
Hijri Astronomical-Base16	GetIslamicCalendar(IslamicLeapYearPattern, IslamicEpoch)(IslamicLeapYearPattern.Base16, IslamicEpoch.Astronomical)
Hijri Astronomical-HabashAlHasib	GetIslamicCalendar(IslamicLeapYearPattern, IslamicEpoch)(IslamicLeapYearPattern.HabashAlHasib, IslamicEpoch.Astronomical)
Persian Simple	PersianSimple
Persian Arithmetic	PersianArithmetic
Persian Algorithmic	PersianAstronomical (see note)
Um Al Qura	UmAlQura()
Hebrew Civil	HebrewCivil
Hebrew Scriptural	HebrewScriptural

The ID "Persian Algorithmic" for the Persian Astronomical calendar is an unfortunate error. The ID has been incorrect in Noda Time for so long that "fixing" it now would cause compatibility issues between systems storing or exchanging Noda Time data.

Ids

Returns the IDs of all calendar systems available within Noda Time. The order of the keys is not guaranteed.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public static IEnumerable<string> Ids { get; }

Property Value

Type	Description
IEnumerable<string>	The IDs of all calendar systems available within Noda Time.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

IslamicBcl

Returns an Islamic calendar system equivalent to the one used by the BCL HijriCalendar.

Since 1.4.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem IslamicBcl { get; }

Property Value

Type	Description
CalendarSystem	An Islamic calendar system equivalent to the one used by the BCL.

Remarks

This uses the Base16 leap year pattern and the Astronomical epoch. This is equivalent to HijriCalendar when the HijriCalendar.HijriAdjustment is 0.

See Also

GetIslamicCalendar(IslamicLeapYearPattern, IslamicEpoch)

Iso

Returns a calendar system that follows the rules of the ISO-8601 standard, which is compatible with Gregorian for all modern dates.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem Iso { get; }

Property Value

Type	Description
CalendarSystem	The ISO calendar system.

Remarks

As of Noda Time 2.0, this calendar system is equivalent to Gregorian. The only areas in which the calendars differed were around centuries, and the members relating to those differences were removed in Noda Time 2.0. The distinction between Gregorian and ISO has been maintained for the sake of simplicity, compatibility and consistency.

Julian

Returns a pure proleptic Julian calendar system, which defines every fourth year as a leap year. This implementation follows the leap year rule strictly, even for dates before 8 CE, where leap years were actually irregular.

Since 1.4.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem Julian { get; }

Property Value

Type	Description
CalendarSystem	A suitable Julian calendar reference; the same reference may be returned by several calls as the object is immutable and thread-safe.

Remarks

Although the Julian calendar did not exist before 45 BCE, this calendar assumes it did, thus it is proleptic. This implementation also fixes the start of the year at January 1.

MaxYear

Gets the maximum valid year (inclusive) within this calendar.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public int MaxYear { get; }

Property Value

Type	Description
int	The maximum valid year (inclusive) within this calendar.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

MinYear

Gets the minimum valid year (inclusive) within this calendar.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public int MinYear { get; }

Property Value

Type	Description
int	The minimum valid year (inclusive) within this calendar.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

Name

Returns the name of this calendar system. Each kind of calendar system has a unique name, but this does not usually provide enough information for round-tripping. (For example, the name of an Islamic calendar system does not indicate which kind of leap cycle it uses.)

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public string Name { get; }

Property Value

Type	Description
string	The name of this calendar system.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

PersianArithmetic

Returns a Persian (also known as Solar Hijri) calendar system implementing the behaviour proposed by Ahmad Birashk with nested cycles of years determining which years are leap years.

Since 2.0.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem PersianArithmetic { get; }

Property Value

Type	Description
CalendarSystem	A Persian calendar system using cycles-within-cycles of years to determine leap years.

Remarks

This calendar is also known as the algorithmic Solar Hijri calendar.

PersianAstronomical

Returns a Persian (also known as Solar Hijri) calendar system implementing the behaviour of the BCL PersianCalendar from .NET 4.6 onwards (and Windows 10), and the astronomical system described in Wikipedia and Calendrical Calculations.

Since 2.0.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem PersianAstronomical { get; }

Property Value

Type	Description
CalendarSystem	A Persian calendar system using astronomical calculations to determine leap years.

Remarks

This implementation uses data derived from the .NET 4.6 implementation (with the data built into Noda Time, so there's no BCL dependency) for simplicity; the actual implementation involves computing the time of noon in Iran, and is complex.

PersianSimple

Returns a Persian (also known as Solar Hijri) calendar system implementing the behaviour of the BCL PersianCalendar before .NET 4.6, and the sole Persian calendar in Noda Time 1.3.

Since 1.4.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem PersianSimple { get; }

Property Value

Type	Description
CalendarSystem	A Persian calendar system using a simple 33-year leap cycle.

Remarks

This implementation uses a simple 33-year leap cycle, where years 1, 5, 9, 13, 17, 22, 26, and 30 in each cycle are leap years.

UmAlQura

Returns an Um Al Qura calendar system - an Islamic calendar system primarily used by Saudi Arabia.

Since 2.0.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem UmAlQura { get; }

Property Value

Type	Description
CalendarSystem	A calendar system for the Um Al Qura calendar.

Remarks

This is a tabular calendar, relying on pregenerated data.

Methods

ForId(string)

Fetches a calendar system by its unique identifier. This provides full round-tripping of a calendar system. This method will always return the same reference for the same ID.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem ForId(string id)

Parameters

Type	Name	Description
string	id	The ID of the calendar system. This is case-sensitive.

Returns

Type	Description
CalendarSystem	The calendar system with the given ID.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

Exceptions

Type	Condition
KeyNotFoundException	No calendar system for the specified ID can be found.
NotSupportedException	The calendar system with the specified ID is known, but not supported on this platform.

See Also

Id

GetAbsoluteYear(int, Era)

Returns the "absolute year" (the one used throughout most of the API, without respect to eras) from a year-of-era and an era.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public int GetAbsoluteYear(int yearOfEra, Era era)

Parameters

Type	Name	Description
int	yearOfEra	The year within the era.
Era	era	The era in which to consider the year

Returns

Type	Description
int	The absolute year represented by the specified year of era.

Remarks

For example, in the Gregorian and Julian calendar systems, the BCE era starts at year 1, which is equivalent to an "absolute year" of 0 (then BCE year 2 has an absolute year of -1, and so on). The absolute year is the year that is used throughout the API; year-of-era is typically used primarily when formatting and parsing date values to and from text.

Exceptions

Type	Condition
ArgumentOutOfRangeException	yearOfEra is out of the range of years for the given era.
ArgumentException	era is not an era used in this calendar.

GetDaysInMonth(int, int)

Returns the number of days in the given month within the given year.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public int GetDaysInMonth(int year, int month)

Parameters

Type	Name	Description
int	year	The year in which to consider the month
int	month	The month to determine the number of days in

Returns

Type	Description
int	The number of days in the given month and year.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

Exceptions

Type	Condition
ArgumentOutOfRangeException	The given year / month combination is invalid for this calendar.

GetDaysInYear(int)

Returns the number of days in the given year.

Since 2.0.x

Availability net6.0, netstandard2.0

Declaration

public int GetDaysInYear(int year)

Parameters

Type	Name	Description
int	year	The year to determine the number of days in

Returns

Type	Description
int	The number of days in the given year.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

Exceptions

Type	Condition
ArgumentOutOfRangeException	The given year is invalid for this calendar.

GetHebrewCalendar(HebrewMonthNumbering)

Returns a Hebrew calendar, as described at https://en.wikipedia.org/wiki/Hebrew_calendar. This is a purely mathematical calculator, applied proleptically to the period where the real calendar was observational.

Since 1.3.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem GetHebrewCalendar(HebrewMonthNumbering monthNumbering)

Parameters

Type	Name	Description
HebrewMonthNumbering	monthNumbering	The month numbering system to use

Returns

Type	Description
CalendarSystem	A Hebrew calendar system for the given month numbering.

Remarks

Please note that support for the Hebrew calendar is somewhat experimental, particularly in terms of calculations involving adding or subtracting years. Additionally, text formatting and parsing using month names is not currently supported, due to the challenges of handling leap months. It is hoped that this will be improved in future versions.

The implementation for this was taken from https://www.cs.tau.ac.il/~nachum/calendar-book/papers/calendar.ps, which is a public domain algorithm presumably equivalent to that given in the Calendrical Calculations book by the same authors (Nachum Dershowitz and Edward Reingold).

GetIslamicCalendar(IslamicLeapYearPattern, IslamicEpoch)

Returns an Islamic, or Hijri, calendar system.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public static CalendarSystem GetIslamicCalendar(IslamicLeapYearPattern leapYearPattern, IslamicEpoch epoch)

Parameters

Type	Name	Description
IslamicLeapYearPattern	leapYearPattern	The pattern of years in the 30-year cycle to consider as leap years
IslamicEpoch	epoch	The kind of epoch to use (astronomical or civil)

Returns

Type	Description
CalendarSystem	A suitable Islamic calendar reference; the same reference may be returned by several calls as the object is immutable and thread-safe.

Remarks

This returns a tabular calendar, rather than one based on lunar observation. This calendar is a lunar calendar with 12 months, each of 29 or 30 days, resulting in a year of 354 days (or 355 on a leap year).

Year 1 in the Islamic calendar began on July 15th or 16th, 622 CE (Julian), thus Islamic years do not begin at the same time as Julian years. This calendar is not proleptic, as it does not allow dates before the first Islamic year.

There are two basic forms of the Islamic calendar, the tabular and the observed. The observed form cannot easily be used by computers as it relies on human observation of the new moon. The tabular calendar, implemented here, is an arithmetic approximation of the observed form that follows relatively simple rules.

You should choose an epoch based on which external system you wish to be compatible with. The epoch beginning on July 16th is the more common one for the tabular calendar, so using Civil would usually be a logical choice. However, Windows uses July 15th, so if you need to be compatible with other Windows systems, you may wish to use Astronomical. The fact that the Islamic calendar traditionally starts at dusk, a Julian day traditionally starts at noon, and all calendar systems in Noda Time start their days at midnight adds somewhat inevitable confusion to the mix, unfortunately.

The tabular form of the calendar defines 12 months of alternately 30 and 29 days. The last month is extended to 30 days in a leap year. Leap years occur according to a 30 year cycle. There are four recognised patterns of leap years in the 30 year cycle:

Origin	Leap years
Kūshyār ibn Labbān	2, 5, 7, 10, 13, 15, 18, 21, 24, 26, 29
al-Fazārī	2, 5, 7, 10, 13, 16, 18, 21, 24, 26, 29
Fātimid (also known as Misri or Bohra)	2, 5, 8, 10, 13, 16, 19, 21, 24, 27, 29
Habash al-Hasib	2, 5, 8, 11, 13, 16, 19, 21, 24, 27, 30

The leap year pattern to use is determined from the first parameter to this factory method. The second parameter determines which epoch is used - the "astronomical" or "Thursday" epoch (July 15th 622CE) or the "civil" or "Friday" epoch (July 16th 622CE).

This implementation defines a day as midnight to midnight exactly as per the ISO calendar. This correct start of day is at sunset on the previous day, however this cannot readily be modelled and has been ignored.

GetMaxYearOfEra(Era)

Returns the maximum valid year-of-era in the given era.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public int GetMaxYearOfEra(Era era)

Parameters

Type	Name	Description
Era	era	The era in which to find the greatest year

Returns

Type	Description
int	The maximum valid year in the given era.

Remarks

Note that depending on the calendar system, it's possible that only part of the returned year falls within the given era. It is also possible that the returned value represents the earliest year of the era rather than the latest year. (See the BC era in the Gregorian calendar, for example.)

Exceptions

Type	Condition
ArgumentException	era is not an era used in this calendar.

GetMinYearOfEra(Era)

Returns the minimum valid year-of-era in the given era.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public int GetMinYearOfEra(Era era)

Parameters

Type	Name	Description
Era	era	The era in which to find the greatest year

Returns

Type	Description
int	The minimum valid year in the given era.

Remarks

Note that depending on the calendar system, it's possible that only part of the returned year falls within the given era. It is also possible that the returned value represents the latest year of the era rather than the earliest year. (See the BC era in the Gregorian calendar, for example.)

Exceptions

Type	Condition
ArgumentException	era is not an era used in this calendar.

GetMonthsInYear(int)

Returns the maximum valid month (inclusive) within this calendar in the given year.

Since 1.4.x

Availability net6.0, netstandard2.0

Declaration

public int GetMonthsInYear(int year)

Parameters

Type	Name	Description
int	year	The year to consider.

Returns

Type	Description
int	The maximum month number within the given year.

Remarks

It is assumed that in all calendars, every month between 1 and this month number is valid for the given year. This does not necessarily mean that the first month of the year is 1, however. (See the Hebrew calendar system using the scriptural month numbering system for example.)

Exceptions

Type	Condition
ArgumentOutOfRangeException	The given year is invalid for this calendar. Note that some implementations may return a month rather than throw this exception (for example, if all years have the same number of months in this calendar system). Failure to throw an exception should not be treated as an indication that the year is valid.

IsLeapYear(int)

Returns whether or not the given year is a leap year in this calendar.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public bool IsLeapYear(int year)

Parameters

Type	Name	Description
int	year	The year to consider.

Returns

Type	Description
bool	True if the given year is a leap year; false otherwise.

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.

Exceptions

Type	Condition
ArgumentOutOfRangeException	The given year is invalid for this calendar. Note that some implementations may return a value rather than throw this exception. Failure to throw an exception should not be treated as an indication that the year is valid.

ToString()

Converts this calendar system to text by simply returning its unique ID.

Since 1.0.x

Availability net6.0, netstandard2.0

Declaration

public override string ToString()

Returns

Type	Description
string	The ID of this calendar system.

Overrides

Object.ToString()

Remarks

Many developers will never need to touch this class, other than to potentially ask a calendar how many days are in a particular year/month and the like. Noda Time defaults to using the ISO-8601 calendar anywhere that a calendar system is required but hasn't been explicitly specified.

If you need to obtain a CalendarSystem instance, use one of the static properties or methods in this class, such as the Iso property or the GetHebrewCalendar(HebrewMonthNumbering) method.

Although this class is currently sealed (as of Noda Time 1.2), in the future this decision may be reversed. In any case, there is no current intention for third-party developers to be able to implement their own calendar systems (for various reasons). If you require a calendar system which is not currently supported, please file a feature request and we'll see what we can do.