I saw a thread on this site before about shooting video during the day and then altering it in post to appear as if it were shot at night. Unfortunately, I cannot find that thread now. Does anyway have any advice on how to do this, or know where that thread is?

A quick search (limited two a couple of forums or just the titles) yielded these threads:

http://www.dvinfo.net/conf/showthread.php?t=14111
http://www.dvinfo.net/conf/showthread.php?t=1776
http://www.dvinfo.net/conf/showthread.php?t=51702
http://www.dvinfo.net/conf/showthread.php?t=21934
http://www.dvinfo.net/conf/showthread.php?t=20434
http://www.dvinfo.net/conf/showthread.php?t=19178
http://www.dvinfo.net/conf/showthread.php?t=12106

Awesome, thank you. I don't know why I couldn't find those.