Every year, Muslims around the world anticipate the sighting of the new crescent moon that signifies the official first day of Ramadan, the ninth month of the Islamic calendar and the most sacred month in Islamic culture.

The start of Ramadan fluctuates each year because the lunar Islamic calendar follows the phases of the moon. The beginning and end of Ramadan are determined by a moon sighting committee in Saudi Arabia. It begins the day after the committee spots the new crescent moon, which can be tricky since it’s quite faint and can be seen for only about 20 minutes. If the moon isn’t visible to the naked eye because of haze or clouds, lunar calculations are used to predict