Isn't Easter early this year? Well yes it is, actually. Easter only falls in March about 22% of the time. More specifically Easter only falls on, or before, March 27th about 10% of the time. If you want a really early Easter you need to wait another three years, because Easter 2008 falls as early as March 23rd (which is stunningly rarely early). But even March 23rd isn't the earliest date that Easter can fall, because that's today, March 22nd. And here's why.
Easter Day falls "on the first Sunday after the first full moon after the spring equinox". This year the springequinox was last Sunday, the next full moon is this Friday, and that makes Easter Day next Sunday. Simple (ish). Except that the church doesn't use the real spring equinox, it uses the date of the spring equinox in 325AD (which was March 20th). And the church doesn't use the real full moon, it uses an approximate one called the Paschal Full Moon, with dates that repeat every 19 years. If (and only if) this Paschal Full Moon falls on Saturday March 21st, then Easter Day can be as early as Sunday March 22nd. I'll leave the full explanation to others (here), but the upshot is that Easter Day can fall on any date from March 22nd (today) to April 25th (5 weeks time) inclusive.
Here's a list of really early Easters, so you can see how rare they really are: Easter on 27th March: last happened 1932, next happens 2016 (but then not again until 2157) Easter on 26th March: last happened 1989, next happens 2062 Easter on 25th March: last happened 1951, next happens 2035 Easter on 24th March: last happened 1940, next happens 2391 [falls on or before this date only 3% of the time] Easter on 23rd March: last happened 1913, next happens 2008 [falls on or before this date only 1½% of the time] Easter on 22nd March: last happened 1818, next happens 2285 [falls on this date only ½% of the time]
10 fantastically geeky Easter date links: