If a song has the name of a day of the week in the title, you should only play it on that day. You should never play it on the day before or day after.
Don't play "Sunday, Bloody Sunday" on Saturday, especially not early Saturday morning when people maybe just not-awake enough to be unsure about which weekend day it is.
Exceptions are allowed, of course, if the song mentions more than one day by name, and "Everybody's Workin' for the Weekend" is appropriate any day of the week.
Oh, and every Monday should include the Boomtown Rats in the playlist, by law.