My official weigh-in day is Saturday morning, first thing. I find I weight my lowest at this time, since I usually sleep an embarassingly-long 10-12 hours on Friday nights (making up for the rest of the week!). I think all that sleep helps me drop to my lowest weight.

Anyway...I change the stats on Monday morning when I get back to work, since I don't check this site over the weekend. If the number is higher than my current stats, I don't change anything. I know it will go back down eventually.