If day and night wont work in the worlds of the game, i thought it would be cool if you were allowed the option of changing what time of day it was in your house. that way, players could change the mood of the house and make some of the decor or houses look cooler. You could have several different times to choose from, like dawn, noon, dusk, or night.
Most MMORPG developers have found that trying to program day and night into any phase of the game was both a programming nightmare and a problem with the themes of various parts of the game. Therefore, it's generally assumed the wizards only quest during the day and that they study and sleep at night.