I'm pretty sure that all that matter is you get a certain quantity and quality of sleep.
You want your body to work through all the different stages(4 + REM I believe. Havn't taken Physchology for 3 years) of sleep, most importantly REM sleep.
If your body is tired, go to sleep... if your not tired yet, stay up... Just make sure you get adequate uninterupted sleep.
Each stage of your sleep gets progressively longer the longer you are have uninterupted sleep... Get as much REM as possible and you will be fine.
Thanks
Ryan