Dear Hadi,
Dear Calendar Question,
Thanks for your question.
The Muslim (Islamic) and Christian calendars are two of the most widely used chronological systems in the world, each with its unique cultural and religious significance. Although both religions acknowledge the figure of Jesus, their calendars have different starting points, structures, and relationships to his life and birth.
The Christian calendar, also known as the Gregorian calendar, is solar-based and was introduced by Pope Gregory XIII in 1582. It was a refinement of the Julian calendar, aiming to correct the drift against the solar year and the timing of Easter. The Christian calendar starts with the birth of Jesus Christ, marking it as year one. This calendar is divided into years, months, and days, with a leap year every four years to account for the extra approximately 0.25 days each year.
Conversely, the Muslim calendar, known as the Hijri or Islamic calendar, is a lunar calendar. It consists of 12 months but is approximately 10 to 12 days shorter than the solar year. The Hijri calendar was established during the caliphate of Umar ibn Al-Khattab, marking the migration (Hijra) of the Prophet Muhammad from Mecca to Medina in 622 AD as its starting point. This event is deemed significant as it marks the formation of the first Muslim community (Ummah) and the beginning of Islam as a structured religion. Because it is a lunar calendar, the Islamic months move throughout the seasons over a 33-year cycle, giving a unique rhythm to religious observances as compared to the fixed seasonal cycle of the solar calendars.
The adoption of the Gregorian calendar across the Muslim world is something that happened over time. For example, Egypt did not adopt its use until 1875, Turkey in 1917, and Saudi Arabia in 2016. The vast majority of Muslim countries currently use the Gregorian calendar for nearly all civil purposes, but still do use the Islamic calendar to mark important religious dates, such as Ramadan, Eid al-Fitr, Hajj, and Eid al-Adha.
In peace.