The first Monday of December when it is acceptable to start playing Christmas music
Sam: why did Tommy get beat?

Jim: oh, he played Christmas music before the first Monday
by 1stoftheweek November 26, 2019
1) The day before work day.

2) The day people start thinking about work.
Bob- "Are you almost done with your project?"
Bob- "Cause, there's a crazy party at Tom's place on Saturday."
Tim- "Pretty much done, won't have to worry about it till first monday. I'll be there."
by Usermin May 26, 2012