Just a little thing I noticed this morning -- the favicon on Google Calendar tabs always shows the day of the month. This morning I came back to my laptop and my calendar tab had been in some kind of sleep state so it read "30". I went and reloaded the page and interestingly, instead of going straight to "1", it went to "31" for half a second and then refreshed itself to "1". Which means there must be some code somewhere that says "increment the day by 1. then check to see if that's correct."
@darius I think there might be a backup (and actually, higher resolution) favicon that always shows "31" (which it used to show every day), and it might have shown that until it completed loading the new one