Reckoning the Date

Because traditions use different calendars, the same festival can fall on different dates from year to year, and movable feasts (Easter, the Islamic festivals, the Hindu festivals set by lunar dates), shift against the civil calendar in ways the entries explain. The reckoning of dates is itself part of a festival's character, tying it to the calendars gathered elsewhere in the atlas.

The holidays group by kind (feasts, fasts, festivals, high holy days and observances), so a reader can compare, for instance, the major fasts of several traditions together.