The Japanese calendar, which is also known as the Wareki calendar, works exactly like the Gregorian calendar, except that the year and era are different.

The Japanese calendar recognizes one era for every emperor's reign. The current era is the Heisei era, which began in the Gregorian calendar year 1989. The era name is typically displayed before the year. For example, the Gregorian calendar year 2001 is the Japanese calendar year Heisei 13. Note that the first year of an era is called "Gannen." Therefore, the Gregorian calendar year 1989 was the Japanese calendar year Heisei Gannen.

This class assigns numbers to the eras as follows:

4	平成 (Heisei)	平 (H, h)	January 8, 1989 to present
3	昭和 (Showa)	昭 (S, s)	December 25, 1926 to January 7, 1989
2	大正 (Taisho)	大 (T, t)	July 30, 1912 to December 24, 1926
1	明治 (Meiji)	明 (M, m)	September 8, 1868 to July 29, 1912

This class handles dates from September 8 in the year Meiji 1 (in the Gregorian calendar, September 8, 1868). Although the Japanese calendar was switched from a lunar calendar to a solar calendar in the year Meiji 6 (1873 of the Gregorian calendar), this implementation is based on the solar calendar only.

Leap years in the Japanese calendar correspond to the same leap years in the Gregorian calendar. A leap year in the Gregorian calendar is defined as a Gregorian year that is evenly divisible by four, except if it is divisible by 100. However, Gregorian years that are divisible by 400 are leap years. A common year has 365 days and a leap year has 366 days.

The Japanese calendar has 12 months with 28 to 31 days each:

1	1月 (Ichigatsu)	January	31	31
2	2月 (Nigatsu)	February	28	29
3	3月 (Sangatsu)	March	31	31
4	4月 (Shigatsu)	April	30	30
5	5月 (Gogatsu)	May	31	31
6	6月 (Rokugatsu)	June	30	30
7	7月 (Shichigatsu)	July	31	31
8	8月 (Hachigatsu)	August	31	31
9	9月 (Kugatsu)	September	30	30
10	10月 (Juugatsu)	October	31	31
11	11月 (Juuichigatsu)	November	30	30
12	12月 (Juunigatsu)	December	31	31

Nigatsu, which is equivalent to the Gregorian calendar month of February, has 29 days during leap years and 28 during common years.

The date January 1, 2001 A.D. in the Gregorian calendar is equivalent to the first day of Ichigatsu in the year Heisei 13 in the Japanese calendar.

If the application is using the System.Globalization.JapaneseCalendar class, DateTime.Parse(string) recognizes the era abbreviations in front of the year. The abbreviation is either the single-character case-insensitive Latin alphabet abbreviation or the single-character Kanji abbreviation.

Each System.Globalization.CultureInfo object supports a set of calendars. The CultureInfo.Calendar property returns the default calendar for the culture, and the CultureInfo.OptionalCalendars property returns an array containing all the calendars supported by the culture. To change the calendar used by a System.Globalization.CultureInfo, the application should set the DateTimeFormatInfo.Calendar property of CultureInfo.DateTimeFormat to a new System.Globalization.Calendar.

Namespace: System.Globalization
Assembly: mscorlib (in mscorlib.dll)
Assembly Versions: 1.0.5000.0, 2.0.0.0, 4.0.0.0