I think theres the first bug report: date calculator fails calculating years between two dates. I think the months and days & maybe the time is calculated right only.
1) Screenshot - Input: http://img339.imageshack.us/img339/6679/1988122301il0.png
1) Screenshot - After Calculate: http://img208.imageshack.us/img208/6300/1988122302fv5.png
Then I've modified the month to
11 instead of
12:
2) Screenshot - After Calculate: http://img46.imageshack.us/img46/398/1988112302cv0.png
I'm using Windows XP Professional SP3 - Hungarian.
(Monday is the first day of the week there, and some other things arent the same as in USA / England, I dunno if it counts... maybe thats or something similar is the problem?)