The Gregorian calendar, used by most western countries, recognizes an extra day at the end of February every four years except centenary years not divisible by 400. However, some cultures use calendars that do not apply the same leap year rules as the Gregorian calendar.
The Chinese leap year has 13 months. A leap month is added to the Chinese calendar about every three years. The name of a leap month is the same as previous lunar month. The leap month’s place in the Chinese calendar varies from year to year. Unlike the Gregorian calendar, 2006 was a leap year in the Chinese calendar.To determine a leap year, calculate the number of new moons between the 11th month in one year and the 11th month in the following year. A leap month is inserted if there are 13 moons from the start of the 11th month in the first year to the start of the 11th month in the next year. The leap month does not contain a principal term (Zhongqi). The Chinese calendar has been used for centuries and observes the movement of the sun, moon and stars.
Like the Chinese calendar, 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. An extra month, Adar I, is added after the month of Shevat and before the month of Adar in a leap year. According to Jewish tradition, Adar is a lucky and happy month.A leap year is referred to in Hebrew as Shanah Me'uberet, or a pregnant year. A Jewish leap year occurs seven times in a 19-year cycle. The 3rd, 6th, 8th, 11th, 14th, 17th, and 19th years are leap years in this cycle.
There are about eight leap years in every 33-year cycle in the Iranian (or Persian) calendar. An extra day is added to the last month in a leap year. Leaps years occur when there are 366 days between two New Year’s days. However, it is not universally accepted that the calendar is solely based on observing the vernal equinox.Leap years usually occur every four years. After every six or seven leap years, the Iranian calendar provides for 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.
The Hindu calendar inserts an extra month, often referred to as Adhika Maas, in a leap year. Adhika 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 tend to occur within a given 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.
In the Islamic Hijri calendar one extra 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 Qur'an. The calendar is based on the Qur'an 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.
The Bahá'í year begins on March 21 and is divided into 19 months of 19 days each, totaling 361 days. Four or five intercalary days are added to raise the number of days to 365, or 366 in leap years. The leap day is inserted in the days of Ayyam-i-ha , a period of intercalary days devoted to fasting preparations, hospitality, charity and gift-giving from February 26 to March 1.
The Ethiopian calendar is very similar to the Egyptian Coptic calendar, which has 13 months. Like the Coptic calendar, the Ethiopian calendar adds an extra day to the end of the year once every four years. The Ethiopian and Coptic calendars consist of 13 months, where the first 12 months each have 30 days and the 13th month has six days in a leap year instead of five days in a standard year.
Greece converted to the Gregorian calendar in 1924, although there is debate that the change may have occurred in 1920 or as early as 1916. There is discussion that some Orthodox Christians prefer to use a revised Julian calendar, where there is a discrepancy with the Gregorian calendar with regard to a leap year that will occur in 2800.