if u add a night time all a player has to do is up his gamma settings and its daylight again!!!!!!!!!!!!!!!!!!!
used to play a game called raven shield and the night maps or maps that had dark places in them where a waste of time as players just upped there gamma so they can see perfectly well even when it was pitch black.
luckly punkbuster added a setting so that you can not have your gamma above a certain limit or you would be kicked from the server.