day, called a tithi. The time it takes the moon to traverse a particular distance is the length of that lunar day. Ekadashi refers to the 11th tithi, or lunar day. The eleventh tithi corresponds to a precise angle and phase of the waxing and waning moon. In the bright half of the lunar month, the moon will be exactly 3/4 full on the start of Ekadashi, and in the dark half of the lunar month, the moon will be 3/4 dark on the start of Ekadashi.

There are usually 24 Ekadashis in a calendar year. Occasionally,