It 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 one day in about 2,500 solar years or 2,570 lunar years. It also deviates up to about one or two days in the short term.
In islam there is 12 Months Which is
A sacred month, so called because battle and all kinds of fighting are forbidden (ḥarām) during this month. Muḥarram includes ‘Āshūrā’, the tenth day.
Supposedly named thus because pre-Islamic Arab houses were empty this time of year while their occupants gathered food. Another account relates that they used to loot the houses of their enemies after defeating them in battle, leaving nothing behind.
the first spring
Also means to graze, because cattle were grazed during this month. Also a very holy month of celebration for many Muslims, as it was the month the Prophet Muhammad was born.
the second spring
the first of parched land
Often considered the pre-Islamic summer. Jumādá may also be related to a verb meaning “to freeze” and another account relates that water would freeze during this time of year.
the last of parched land
This is the second sacred month in which fighting is forbidden. Rajab may also be related to a verb meaning “to remove”, so called because pre-Islamic Arabs would remove the heads of their spears and refrain from fighting.
Marked the time of year when Arab tribes dispersed to find water. Sha‘bān may also be related to a verb meaning “to be in between two things”. Another account relates that it was called thus because the month lies between Rajab and Ramaḍān.
Burning is related to fasting as in empty stomach one’s worldly desire will burn. Supposedly so called because of high temperatures caused by the excessive heat of the sun. Ramaḍān is the most venerated month of the Hijri calendar. During this time, Muslims must fastfrom pre-dawn till sunset and should give charity to the poor and needy.
She-camels would normally be in calf at this time of year and raise their tails.
the one of truce/sitting
This is a holy month during which war is banned. People are allowed to defend themselves if attacked.
the one of pilgrimage
During this month Muslim pilgrims from all around the world congregate at Mecca to visit the Kaaba. The Hajj is performed on the eighth, ninth and the tenth of this month. Day of Arafah takes place on the ninth of the month. Eid al-Adha, the “Festival of the Sacrifice”, begins on the tenth day and ends on sunset of the twelfth, and during which war is banned.