Moon sighting is a key part of Muslim life – how the lunar cycle determines the start of Ramadan and Eid

Each year as Ramadan approaches, more than 2 billion Muslims around the world prepare for a month of fasting, prayer and communality. But Ramadan does not begin on the same day everywhere in the world.

This year, some countries will commence the month of fasting on Thursday, February 19, whereas other countries may begin it a day earlier. Similarly, at the end of Ramadan, different communities will celebrate Eid on different dates.

The reason for this lies in the nature of the lunar visibility calendar ...