Thirty-one songs that feature a day as the first word in their title made the Billboard Top-100 charts between 1955 and 1999. This figure does not include alternate versions of the same song.
Thursday is the orphan. It did not make the list.
Monday, Tuesday and Wednesday had 1 song each.
Friday was more popular, with 3 songs.
Sunday scored an even dozen.
The winner is Saturday, with a lucky 13 songs on the list. Artists with Saturday songs include The Drifters, Earth Wind & Fire, Chicago, Lynyrd Skynyrd and Elton John.
Here’s a rocking example: https://youtu.be/XNT6bwrvIzY