I work weekdays 0:20 - 7:30, but I totally change my sleeping habits for the weekend in order to synchronize myself to "normal" people.
When my week's over (Friday morning), I usually don't sleep until Friday night (though I'm going to bed quite early) if I don't have anything planned after supper. Else I try to get some sleep during the day to last longer. I'm living during the days and sleeping at nights all weekend, I don't have the habit of sleeping Sunday nights before going to work, though sometimes I try and get 3-4 hours right before I leave, depending how tired I am.
On weekdays, I sleep from around 1-3PM to 9:30. If I get to bed too early and I somehow awake, I have a hard time getting back to sleep, so I wait to be more tired.