An annual national & bank holiday celebrated within the UK on December 12th, where all gyms are closed so people can engage in science activities to commemorate Bill Nye's day of birth.
Phrase used after repeated alterations of "ur mum gay" have been used. Saying this phrase while simultaneously singing along with the theme of Bill Nye the Science Guy results in the God of Gender Judgement,John Cena, to obey 3 requests to permanently change a person's gender, thus never letting anyone identify them as something else again.