Canceled vs. Cancelled

The first 9 years of my education was in a British setting, and so I spelled a lot of words the British way. When I switched to an American school in 2002, I took a lot of that spelling with me. Some words I adapted rather quickly, but others I have been reluctant to change. One such example of the latter is "favo[u]rite", because the British version has all five vowels (maaah).

An cool phenomenon I recently discovered is that my journal shows when I adopted certain words. The word in question is "cancel[l]ed"; a quick search of my journal gives the following:

$ ./tools -Sd cancelled
2003-04-29
2003-08-26
2003-10-15
2003-12-01
2004-01-07
2004-02-12
2004-03-10
2004-04-02
2004-10-27
2005-03-29
2006-04-14
2006-08-14
$ ./tools -Sd canceled
2003-09-01
2005-11-21
2007-02-14
2007-03-30
2007-04-16
2007-04-18
2007-05-25
2007-10-07
2008-01-05
2008-04-05
2008-04-08
2008-04-29
2008-05-31
2008-06-07

A quick glance shows that all the way through 2006 I used the British version, and the in 2007 I abruptedly changed to the American version. The only disrepancy this theory leaves is the single uses of the American version in 2003 and 2005. I guessed, correctly, to be quotes I put in from other people.