Muslims prepare for Ramadan, a month of fasting, prayer, and reflection, starting at sunset Friday and ending March 30. Follow Newsweek's live blog.

Ramadan is not uniformly observed globally — the start date can vary by country or even be different mosque to mosque in the same city for a variety of reasons. But it all starts with a sighting of the crescent moon.

However, unlike other religious holidays, Ramadan doesn't start on the same day each year. This is because the Islamic calendar follows the moon's cycle. And what can be even more confusing is that different groups might give slightly different dates for when Ramadan starts,