What This Calculator Does
The Days Until Easter Calculator finds the exact date of Easter Sunday for any year and counts how many days remain from today. It uses the Computus — the centuries-old method the Church uses to fix Easter — implemented as the well-known anonymous Gregorian (Western) algorithm. This tool follows the Western Christian calendar used by Catholic and most Protestant churches; Eastern Orthodox Easter often falls on a different date and is not computed here.
How to Use It
Enter a year (1583 or later, the start of the Gregorian calendar) and submit. You'll see the date of Easter Sunday for that year and the number of days from today until that date. A negative number means Easter has already passed this year — enter next year to count down to the next one.
The Formula Explained
Easter falls on the first Sunday after the first ecclesiastical full moon on or after March 21. Rather than tracking the moon directly, the Computus uses modular arithmetic on the year. Intermediate values (the golden number, century corrections, the epact h, and the weekday factor l) combine into a single expression: \((h + l - 7m + 114)\). Dividing by 31 gives the month (3 = March, 4 = April) and the remainder plus one gives the day. The day count is then simply the Easter date minus today's date.
$$\begin{gathered} \text{Days Until Easter} = \frac{\text{Easter}(\text{Year}) - \text{Today}}{86400000\ \text{ms/day}} \\[1.5em] \text{where Easter month \& day come from the Gregorian Computus:} \\[0.5em] \left\{ \begin{aligned} \text{Month} &= \left\lfloor \frac{h + \ell - 7m + 114}{31} \right\rfloor \\ \text{Day} &= \left[(h + \ell - 7m + 114) \bmod 31\right] + 1 \end{aligned} \right. \end{gathered}$$
Worked Example
For the year 2024, the algorithm yields month = 3 and day = 31 — so Easter Sunday is March 31, 2024. If today were March 1, 2024, the countdown would read 30 days. For 2025 the result is April 20, 2025.
$$\text{Days Until Easter} = \frac{\text{Mar 31, 2024} - \text{Mar 1, 2024}}{86400000\ \text{ms/day}} = 30\ \text{days}$$
FAQ
Why must the year be 1583 or later? The Gregorian calendar (and this Computus variant) began in October 1582, so earlier dates would not be meaningful.
Does this give Orthodox Easter? No. It computes the Western (Gregorian) date. Orthodox churches use the Julian calendar, which usually produces a later date.
Can Easter fall in March? Yes — it ranges from March 22 to April 25 depending on the lunar cycle.
