1) Pertains to the marked days of a woman's bleeding "period" within the
menstrual cycle, from the beginning to the end.
2) "Happy Red Flag Day" is a phrase often used in
woman code to welcome one-another into the relentless, ceremonial unleashing of hell about life's problems, onto the ears of the unwilling-- mainly men. You may see this act
transpire on Facebook with 12 guys asking "what does red flag day mean,'' followed by 37 "likes" on the initial post. The best means of avoiding this outcome is to remain silent and do not (repeat) DO NOT engage in dialog.
Girl 1: Hey youuu, happy
Red Flag Day.
Girl 2: God, I know. I just want it to be over!
Guy 1: What
red flag day?
Girl 2: You never listen to me, EVER! I'm leaving... ASSHOLE ::slams door::
Guy 1: ...What!?
What the hell was that about?