Don't know anything about the Synod of Whitby (664*)? Heavenfield has a nice summary and commentary on it. If that's not enough Whitbylicousness to satisfy you, try the Answers.com page or find out what the Catholics say about it vs. what the Anglicans say about it.
Of course, even better is to read Bede's Ecclesiastical History of the English Nation** and watch Bede get worked up into a froth over the date of Easter.
*Note the comments below; in the original post, I got distracted and meant to type the phrase "(in 664 -- as Heavenfield points out, 1343 years ago)" but instead just typed 1343 as if it happened in A.D. 1343. This would have made Bede's Ecclesiastical History a miracle of time travel.
**I know it's translated "Ecclesiastical History of the English People" in the linked Penguin edition, but what's the use of being a medieval lit professor if I can't get all persnickety about such issues?