blue Monday
US /bluː ˈmʌn.deɪ/
UK /bluː ˈmʌn.deɪ/

1.
lundi morose, blues du lundi
a feeling of sadness or depression experienced on a Monday, especially after a weekend of rest or enjoyment
:
•
I always get that blue Monday feeling after a long holiday.
J'ai toujours ce sentiment de lundi morose après de longues vacances.
•
Despite the sunny weather, it was a real blue Monday for him.
Malgré le temps ensoleillé, c'était un vrai lundi morose pour lui.