Approximate year & different calendars (Gregorian, Julian, Hebrew, ...)

The Julian Calendar class recognizes only the current era.

Unlike the Gregorian calendar, the Julian calendar defines a leap year as a year that is evenly divisible by four with no exceptions; therefore, the calendar is inaccurate by one day every 128 years. A common year has 365 days and a leap year has 366 days.

The date January 1, 2001 A.D. in the Gregorian calendar is equivalent to the 19th day of December in the year 2000 A.D. in the Julian calendar.

The Hebrew Calendar recognizes two eras: B.C.E. (before the common era) and A.M. (Latin "Anno Mundi", which means "the year of the world"). This implementation of the HebrewCalendar class recognizes only the current era (A.M.) and the Hebrew years 5343 to 5999 (1583 to 2239 in the Gregorian calendar).

In every 19-year cycle that ends with a year that is evenly divisible by 19, the 3rd, 6th, 8th, 11th, 14th, 17th, and 19th years are leap years. A common year can have from 353 to 355 days, depending on the placement of Jewish holidays. A leap year can have from 383 to 385 days.

The Hijri Calendar recognizes one era: A.H. (Latin "Anno Hegirae", which means "the year of the migration," in reference to the migration of Muhammad from Mecca).

In every 30-year cycle that ends with a year that is evenly divisible by 30, the 2nd, 5th, 7th, 10th, 13th, 16th, 18th, 21st, 24th, 26th, and 29th years are leap years. A common year has 354 days and a leap year has 355 days.

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.

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.

The Korean Calendar works exactly like the Gregorian calendar, except that the year and era are different.

The date January 1, 2001 A.D. in the Gregorian calendar is equivalent to the first day of January in the year 4334 of the current era in the Korean calendar.

The Taiwan Calendar works exactly like the Gregorian calendar, except that the year and era are different. The TaiwanCalendar class recognizes only the current era.

The date January 1, 2001 C.E. in the Gregorian calendar is equivalent to the first day of January in the year 90 of the current era in the Taiwan calendar.

The ThaiBuddhistCalendar works exactly like the Gregorian calendar, except that the year and era are different.

The date January 1, 2001 A.D. in the Gregorian calendar is equivalent to the first day of January in the year 2544 of the current era in the Thai Buddhist calendar.