rag week

noun2

1. •
   (UK, Ireland) An annual event in many universities where students engage in unusual activities to raise money for charity.

   • The only acting that looks like anything but rag week at a bad university is by Billy Hartman as a private detective. — 1982
2. •
   (slang, vulgar) The days of the month when a woman has her period.

   • I wouldn't bother trying to get off with her – it's rag week.