Why Ramadan moves about 11 days earlier every year
The Islamic calendar follows the moon, not the sun, so Ramadan travels through every season in about 33 years.
The Gregorian calendar follows the sun: 365 or 366 days, keeping the seasons in place. The Islamic calendar follows the moon: twelve lunar months, a year of 354 or 355 days.
The 11-day drift
Because the lunar year is about 11 days shorter, every Islamic date arrives about 11 days earlier each year in the Gregorian calendar. Ramadan, the month of fasting from dawn to sunset, moves through the seasons:
- In some decades it falls in summer, with long, hot days of fasting.
- About 15 years later it falls in winter, with short days.
- After about 33 years it is back where it started.
So someone who fasts for most of their life experiences Ramadan in every season, more than once.
Watching for the moon
Traditionally, each month begins with the sighting of the new crescent moon (hilal). Clouds, location and different religious authorities mean that Ramadan and Eid can begin on different days in different countries, which is why the start date is often announced only the night before. Some communities now use astronomical calculations instead.
Counting from the Hijra
Year 1 of the calendar starts with the Hijra, Muhammad’s migration from Mecca to Medina in 622 CE. Years are marked AH, Anno Hegirae. In much of the Muslim world, the Hijri calendar is used for religious life alongside the Gregorian calendar for civil purposes.
Bring it up
“Ramadan moves about 11 days earlier every year, so someone who lives to 66 will fast through every season twice.”
Follow the thread
- In contrastWhy Christmas is on 25 December A festival fixed to the sun’s calendar, versus one that follows the moon.
- RelatedJesus was probably born “Before Christ” Calendars count from founding events: the Hijra in 622, or the Incarnation.
- RelatedChina spans five time zones but uses one Calendars and clocks are human agreements laid over astronomy.
