The Islamic Calendar, also known as the Hijri or lunar calendar, began on July 16, 622 CE, marking the first day of the first year of the Hegira (Hijra). This significant event commemorates the migration of the Prophet Muhammad from Mecca to Medina, a pivotal moment in Islamic history that not only shaped the early Muslim community but also established a new chronological framework for Muslims. The calendar is based on lunar months, consisting of 12 months in a year, with each month being either 29 or 30 days long, leading to a total year length of approximately 354 or 355 days.

As a result, Islamic dates shift annually in relation to the Gregorian calendar, which is solar-based, causing Islamic holidays to occur on different Gregorian dates each year. The Islamic Calendar is used primarily for religious purposes, helping to determine the dates of significant events such as Ramadan and Hajj. Understanding the start of the Islamic Calendar provides insight into the cultural and historical context of the Islamic faith and its community practices.