Montag, because the moon is shining on mondays.
Dienstag, because your servitude to the labor force heightens on the second day of work.
Mittwoch, because it's the middle of a work week.
Donnerstag, because thursdays mark the beginning of the storm.
Freitag, because it's your final day for work and you'll be set free after today.
Samstag, because the age of consent in Germany is 14.
Sonntag, because you'll be sleepier on this day than on saturday due to having work tomorrow.