Monday
Some things are hard to differentiate, and some are not. Like Mondays. It's easy to know it's Monday.
My guess is although I haven't googled to find out there are probably many Monday poems. Not Tuesdays or Thursdays. Wednesday has a chance. Friday Saturday Sunday yes. My guess is we could find out pretty easily my guess is people have said its Monday with despair very occasionally there's an on boy Monday poem. As for me I always like poets who say as for me because The Good Wife was on last night after a Full Long Weekend now I know today is oh no Monday.