Advanced Easter Date & Countdown
Calculate the exact date of Easter Sunday for any year and see the precise countdown, based on the Gregorian calendar rules.
The Rule of the Paschal Full Moon
Easter Sunday, the most important feast in the Christian calendar, is a **moveable feast**, meaning its date changes every year. Unlike fixed holidays, its date is determined by a set of astronomical and ecclesiastical rules established at the First Council of Nicaea in 325 AD.
The Gregorian Calculation (Western Christianity)
The date of Easter is defined as the **first Sunday after the ecclesiastical Full Moon** that occurs on or next after **March 21** (the date of the Spring Equinox for ecclesiastical purposes).
- **Paschal Full Moon:** This is the ecclesiastical full moon, which may differ slightly from the actual astronomical full moon.
- **The earliest date** Easter can fall is **March 22**.
- **The latest date** Easter can fall is **April 25**.
How the Algorithm Works
The calculation used by this tool is a version of the **Meeus/Butcher's Algorithm**, which uses modular arithmetic to simulate the lunar and solar cycles without needing complex astronomical tables. It precisely determines the date of the Paschal Full Moon and then finds the next Sunday. The elegance of the algorithm is how it mathematically incorporates the 19-year lunar cycle (Metonic cycle) to predict the moon's phase, allowing for a precise annual calculation.