What the Days Until Easter Monday Calculator does
Easter Monday is the public holiday that falls on the day immediately after Easter Sunday. Because Easter is a movable feast, its date changes every year, so a fixed-date countdown will not work. This calculator computes the exact date of Easter Monday for any year using the standard Gregorian Easter algorithm (the Computus), then counts the whole days between the date you enter and that Easter Monday.
The result is a signed number of days: a positive value means Easter Monday is still ahead of your chosen date, and a negative value means it has already passed for that year.
How to use it
Enter the year you are interested in and the date you want to count from (it defaults to today). The tool first finds Easter Sunday for that year with the Computus, adds one day to get Easter Monday, and then reports how many days separate your chosen date from that holiday. It also shows the calendar dates of both Easter Sunday and Easter Monday so you can see the full Easter weekend at a glance.
The formula explained
Easter Monday is defined as one day after Easter Sunday:
$$ \text{Easter Monday} = \text{Easter Sunday} + 1 \text{ day} $$Easter Sunday itself is found with the Anonymous Gregorian algorithm. For a year Y, compute:
$$ a = Y \bmod 19, \quad b = \lfloor Y / 100 \rfloor, \quad c = Y \bmod 100 $$ $$ d = \lfloor b / 4 \rfloor, \quad e = b \bmod 4, \quad f = \lfloor (b + 8) / 25 \rfloor $$ $$ g = \lfloor (b - f + 1) / 3 \rfloor, \quad h = (19a + b - d - g + 15) \bmod 30 $$ $$ i = \lfloor c / 4 \rfloor, \quad k = c \bmod 4, \quad l = (32 + 2e + 2i - h - k) \bmod 7 $$ $$ m = \lfloor (a + 11h + 22l) / 451 \rfloor $$The month and day of Easter Sunday are then
$$ \text{month} = \lfloor (h + l - 7m + 114) / 31 \rfloor $$ $$ \text{day} = \left( (h + l - 7m + 114) \bmod 31 \right) + 1 $$where a month value of 3 means March and 4 means April. Adding one day to this date gives Easter Monday, and the countdown is the difference in whole days between it and your chosen date.
Worked example
Take the year 2025 counting from 1 January 2025. Running the Computus gives Easter Sunday on 20 April 2025, so Easter Monday is 21 April 2025. The number of days from 1 January to 21 April is 31 (January) + 28 (February) + 31 (March) + 20 (April) = 110 days. The calculator therefore reports 110 days until Easter Monday.
Frequently asked questions
Is Easter Monday always the day after Easter Sunday? Yes. Easter Monday is fixed as the Monday immediately following Easter Sunday, so it is always exactly one day later in the Western (Gregorian) calendar.
Why does the date of Easter Monday change every year? Easter Sunday is a movable feast set as the first Sunday after the first ecclesiastical full moon on or after 21 March. Because that full moon shifts against the calendar, Easter, and therefore Easter Monday, lands on a different date each year, ranging from late March to late April.
Does this calculator use the Western or Orthodox date? It uses the Western (Gregorian) Easter given by the Anonymous Gregorian Computus, the date observed in Roman Catholic and most Protestant traditions. Orthodox churches that follow the Julian calendar can celebrate on a different day.
