Period or not that is uncalled for. You need to leave. That will get real old and annoying in time. Find someone who can, although they are on their cycle, manage their emotions properly.

Survival guide to a girlfriend's period: first, start a calendar of your girlfriend's cycle and keep it under lock and key. Second, periods are like fight club; you don't talk about them. Leave that to the experts (the girls). Third, always keep the following handy: two of your girlfriend's sanitary pads (one for her, one to know which ones to buy for her), two of your girlfriend's tampons (same), a bar of chocolate, a bottle of Tylenol or Advil, coupons for a pizza, a hot pad. You may ask your girlfriend what kind of chocolate or pizza she likes. This way, you will be like a boy scout, always ready, and ready to scout for a girlfriend who doesn't throw china at your head.

Mate time for a break up that is uncalled for and a bad sign.

What if I, a young woman, told a similar story from my perspective? "Today, I asked my new boyfriend if he was feeling alright, since he was in a bad mood for the first time since we started dating because of problems he had with his boss. I got an empty cereal bowl thrown at my head. Question asked and answered." Does anyone think this is funny if the genders were reversed?

Uhhh, no. You don't actually have to put up with that. I do have bad period days too, but that means I'm just a grumpy lump on the couch who watches too much TV and is very thankful for every snack placed in my lap I don't have to move for. But it's not an excuse for violent, disrespectful behavior. It's one thing to say "I don't feel good and I just need a snooze day/ a movie marathon where I can just be snarky towards the characters/ a fast food orgy" but it's not a justification to completely fly off the handle like that.

Periods make you a little grumpy and impatient, not physically abusive. GTFO

If she’s doing that at the BEGINNING of the relationship, imagine what she’ll do later on?? This is supposed to be the honeymoon period. Get outta there.

I hope you mean EX-girlfriend. That way, I could say, “Man, you dodged a cereal bowl there!”

Yeah you need to leave. I get extremely painful period and I've never assaulted my partner over it. I may be moody but that doesn't go beyond that. Girls who use their period as an excuse to be abusive shouldn't be in a relationship.

Leave her. That's not normal behavior.