The Islamic leap year

The Islamic leap year

The tabular Islamic Hijri calendar has 11 leap years in a 30-year cycle. An extra day is added to the last month of the year during the Islamic leap year.

The Muslim pilgrimage to Mecca in Hajj.

A leap day is added

During a leap year 1 day is added to the last month, making it 30 days instead of 29 days, in a leap year. This month, Dhu l-Hidjdja, is also referred to as the month of the Hajj � the Muslim pilgrimage to Mecca. The Hijri calendar has a 30-year cycle with 11 leap years of 355 days and 19 years of 354 days. In the long term, it is accurate to about one day in 2500 years.

The leap year occurs in the 2nd, 5th, 7th, 10th, 13th, 16th, 18th, 21st, 24th, 26th and 29th years of the 30-year cycle. Leap months are forbidden by the Quran. The calendar is based on the Quran and its proper observance is a sacred duty for Muslims. It is a purely lunar calendar and contains 12 months that are based on the moon�s motion.

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The Iranian leap year

The Iranian leap year

The Iranian or Persian calendar has about 8 leap years in a 33-year cycle. An extra day is added to the last month in a leap year.

Iranian flag over Teheran, Iran.

Calculating the leap year

Leap years usually occur every four years. After every six or seven leap years, the Iranian calendar includes a leap year that occurs on the fifth year instead of the fourth year. A period of 2820 years was the base for calculations to establish the frequency of a leap year occurring on the fifth year. At the start and the end of the 2820-year cycle, the vernal equinox takes place exactly at the same time of the tropical year.

The Iranian calendar dates back to the 11th century, when a panel of scientists created a calendar that was more accurate than other calendars at the time. Although some changes have been made to the calendar, it is slightly more accurate than the Gregorian calendar. Compared with the Gregorian calendar, which errors by one day in about every 3226 years, the Iranian calendar needs a one-day correction in about every 141,000 years.

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The Jewish Leap Year

The Jewish Leap Year

The Jewish leap year has 13 months and occurs 7 times in a 19-year cycle.

The Jewish leap year has 13 months.

The Jewish calendar has 13 months in a leap year. There are 29 or 30 days in each month in a Jewish leap year, which has 383, 384, or 385 days.

Adar � the lucky month

An extra month, Adar I, is added after the month ofShevat and before the month of Adar in a leap year. The month is also known as Adar Rishon or Adar Alef. According to Jewish tradition, Adar is a lucky and happy month. A leap year is referred to in Hebrew as Shanah Meuberet, or a pregnant year. A Jewish leap year occurs 7 times in a 19-year cycle. The 3rd, 6th, 8th, 11th, 14th, 17th, and 19th years are leap years in this cycle.

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The Hindu leap year

The Hindu leap year

The Hindu leap year has an extra month and occurs once every 3 years or 4 times in 11 years.

Hindu festivals are celebrated around the Hindu Leap month, Adhik Maas.

The Hindu calendar includes an extra month, often referred to as �Adhik Maas� in a leap year. �Adhik Maas� typically occurs once every three years or four times in 11 years.

Therefore the yearly lag of a lunar year is adjusted every three years. This adjustment allows for Hindu festivals to take place within a given time span rather than on a set day.

The Indian National Calendar and the Revised Bangla Calendar of Bangladesh organize their leap years so their leap day is close to February 29 in the Gregorian calendar.

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