movable feast

The phrase "movable feast" typically refers to a religious observance or holy day that does not have a fixed date but instead varies from year to year based on the position of the moon or other astronomical events. This term is commonly used in Christian traditions, particularly in reference to Easter, which is considered the most prominent movable feast. The date of Easter changes each year, falling on the first Sunday following the first full moon after the vernal equinox. Other examples of movable feasts include holidays such as Passover and Ramadan, which are determined by different lunar calendars in Judaism and Islam, respectively.