This interesting bit was posted as "the latest news" on the NASA website:

STS-129 Mission Specialists Mike Foreman and Randy Bresnik, set to perform the second spacewalk of the mission Saturday, are spending the night in the Quest airlock as part of the overnight “campout” procedure that helps purge nitrogen from their bloodstreams, preventing decompression sickness once they move out into the vacuum of space.
The International Space Station crew is scheduled to go to sleep at 6:58 p.m. EST, and the shuttle crew heads to bed a half hour later. Both crews are set to wake up Saturday at 3:28 a.m. The spacewalk is slated to begin at 8:18 a.m.

The astronauts have to go to bed at 6:58 PM (not 7 PM, but 6:58 PM) - and they have to wake up in the middle of the night.  In addition it takes 5 hours to get ready for a walk outside :) and you even have to sleep in the mudroom before you can head out.  Not an easy job, being an astronaut.