• Easter Day always falls on the first Sunday after the first full moon after the Spring equinox. For example, this year the Spring equinox was on March 21st, but the next full moon wasn't until last Wednesday (April 16th), so Easter ended up being today (April 20th). Well, that's the simplified version. There is a much more complicated rule, but let's not go into it here.
• The rules governing Easter were decided by the Council of Nicæa in AD 325.
• Easter moves around so much because the rules are based on the date of the Jewish fewish festival of Passover.
• Easter Sunday always falls within the range March 22nd to April 25th inclusive - that's 35 possible dates. see table • Easter last fell on the earliest possible date in 1818, and will next fall on March 22nd in 2285.
• Easter last fell on the latest possible date in 1943, and will next fall on April 25th in 2038.
• Within the next ten years we do get to experience Easter on March 23rd (2008) and April 24th (2011).
• March 22nd is the least likely date for Easter to fall - this happens in less than ½% of years. see graph • April 19th is the most likely date for Easter to fall - this happens in nearly 4% of years.
• You've probably never experienced Easter on April 20th before because this last happened in 1930, but Easter will be on this date again in 2014 and 2025.
• Almost exactly half of Easter dates occur on the same date 11 years later (but never more than 4 in a row). For example, Easter will be on April 21st in 2019, 2030, 2041 and 2052 but not in 2063.
• Easter falls on April 8th in both 2007 and 2012, a gap of five years. No shorter interval is possible.
• Consecutive Easters are always always separated by 350, 357, 378, or 385 days (that's 50, 51, 54, or 55 weeks). For example, Easter 2003 is 385 days after Easter 2002, but 357 days before Easter 2004.
Here's a table showing the date of Easter from 1900-2099 (via this site)
If there's a digit in the table then Easter is in March, and that's the last digit of the date (22nd-31st).
If there's a letter in the table then Easter is in April, and the letter follows the code a=1, b=2, c=3 etc.
For example, the symbol in the table for 2003 is a letter, so Easter is in April. That letter is the letter t, which is the 20th letter of the alphabet, so Easter is on April 20th.