

Rents, salaries, and other comparable recurring obligations are typically paid according to the civil calendar.

Iran and Afghanistan are notable outliers to this rule, as they follow the Solar Hijri calendar. The Gregorian calendar is used in virtually all nations where Islam is a major religion, with Syriac month-names used in the Levant and Mesopotamia (Iraq, Syria, Jordan, Lebanon, and Palestine). It is therefore an important part of Islam. It is used to establish the correct dates of Islamic holidays and ceremonies, such as the yearly fasting period (the month of Ramadan) and the right time for the Hajj (the pilgrimage to Mecca, Saudi Arabia).

The year is of twelve months, out of which four months are sacred: Three are in subsequent Dhu al-Qadah, Dhu al-Hijjah, and Muharram, and (the fourth is) Rajab of (the tribe of) Mudar which comes between Jumada-Thaniyah and Sha’ban." The Prophet Muhammad (PBUH) is reported to have said: "The division of time has turned to its original form which was current when Allah created the Heavens and the Earths.

The respect and importance of these months predates Islam with the Arabs refraining from fighting during these months tracing back from the laws of Abraham A.S. During these months, fighting and waging war is forbidden, and all disputes are to be resolved peacefully. These months are considered to be of great importance in Islamic tradition and culture, and are treated differently from the other months. The four sacred months of the Hijri calendar are Rajab, Dhu al-Qadah, Dhu al-Hijjah, and Muharram. And know that Allah is with those mindful ˹of Him˺” And together fight the polytheists as they fight against you together. So do not wrong one another during these months. Allah (SWT) States: “ Indeed, the number of months ordained by Allah is twelve-in Allah’s Record since the day He created the heavens and the earth-of which four are sacred. The months are based on the phases of the moon and are named Muharram, Safar, Rabi al-Awwal, Rabi al-Thani, Jumada al-Ula, Jumada al-Akhirah, Rajab, Shaban, Ramadan, Shawwal, Dhu al-Qadah, and Dhu al-Hijjah. The Hijri calendar, also known as the Islamic calendar, is a lunar calendar consisting of 12 months in a year of 354 or 355 days.
