It is actually quite easily done:
see http://aa.usno.navy.mil/faq/docs/easter.php
Computing the Date of Easter
The rule is that Easter is the first Sunday after the first ecclesiastical full moon that occurs on or after March 21. The lunar cycles used by the ecclesiastical system are simple to program. The following algorithm will compute the date of Easter in the Gregorian Calendar system.
The algorithm uses the year, y, to give the month, m, and day, d, of Easter. The symbol * means multiply.
Please note the following: This is an integer calculation. All variables are integers and all remainders from division are dropped. For example, 7 divided by 3 is equal to 2 in integer arithmetic.
c = y / 100
n = y - 19 * ( y / 19 )
k = ( c - 17 ) / 25
i = c - c / 4 - ( c - k ) / 3 + 19 * n + 15
i = i - 30 * ( i / 30 )
i = i - ( i / 28 ) * ( 1 - ( i / 28 ) * ( 29 / ( i + 1 ) )
* ( ( 21 - n ) / 11 ) )
j = y + y / 4 + i + 2 - c + c / 4
j = j - 7 * ( j / 7 )
l = i - j
m = 3 + ( l + 40 ) / 44
d = l + 28 - 31 * ( m / 4 )
For example, using the year 2010,
y=2010,
c=2010/100=20,
n=2010 – 19 x (2010/19) = 2010 – 19 x (105) = 15, [see note above regarding integer calculations]
etc. resulting in Easter on April 4, 2010.
The algorithm is due to J.-M. Oudin (1940) and is reprinted in the Explanatory Supplement to the Astronomical Almanac, ed. P. K. Seidelmann (1992). See Chapter 12, “Calendars”, by L. E. Doggett.
The following are dates of Easter from 1980 to 2024:
1980 April 6 1995 April 16 2010 April 4
1981 April 19 1996 April 7 2011 April 24
1982 April 11 1997 March 30 2012 April 8
1983 April 3 1998 April 12 2013 March 31
1984 April 22 1999 April 4 2014 April 20
1985 April 7 2000 April 23 2015 April 5
1986 March 30 2001 April 15 2016 March 27
1987 April 19 2002 March 31 2017 April 16
1988 April 3 2003 April 20 2018 April 1
1989 March 26 2004 April 11 2019 April 21
1990 April 15 2005 March 27 2020 April 12
1991 March 31 2006 April 16 2021 April 4
1992 April 19 2007 April 8 2022 April 17
1993 April 11 2008 March 23 2023 April 9
1994 April 3 2009 April 12 2024 March 31