Apara Ekadashi

Ekadashi is the eleventh day of a lunar fortnight, so it comes twice a lunar month — once while the Moon is waxing, once while it wanes. Each of the twenty-four has its own name, taken from the lunar month it falls in.

This one falls in the dark fortnight, while the Moon is emptying.

It is traditionally kept as a light day — a fast, or simply less of everything. The date is set by the lunar day at sunrise where you are, so a local calendar may name the day either side of this one.