(c++) Easter Sunday is the first Sunday after the first full moon of spring. To compare the date, you can use this algorithm invented in 1800:

1. Let y be the year (such as 1975
2. Divide y by 19 and call the remainder a. Ignore the quotient
3. Divide y by 100 to get quotient b and remainder c
4. Divide b by 4 to get a quotient d and remainder e
5. Divide 8*b+13 by 25 to get a quotient g. Ignore remainder
6. Divide 19 * a + b d g + 15 by 30 to get remainder h. Ignore quotient
7. Divide c by 4 to get quotient j and remainder k
8. Divide a + 11 * h by 319 to get quotient m. Ignore remainder
9. Divide 2 * e + 2 * j k + m + 32 by 7 to get remainder r. Ignore quotient
10. Divide h m+r+90 by 25 to get quotient n. Ignore remainder
11. Divide h- m + r+ n +19 by 32 to get remainder p. Ignore quotient

Then Easter falls on day p of month n. For example, if y is 2001,

A=6 b=20 c= 1 d=5 e=0 g=6 h =18 j=0 k=1 m=0 n=4 r =6 p=15. Therefore in 2001, Easter fell on April 15