Well, not "everywhere." PMS -- that is, the part where women turn into uncontrollable rage-monsters -- only affects women in Western society.
Anthropologists and psychologists increasingly view PMS as a culture-bound syndrome. This means it's a psychosomatic condition that only occurs within a particular culture -- in this case, Western culture. Sure, women in all times and places have had the physical symptoms ... but not the emotional/psychological ones. In fact, none of the hormonal changes that take place should influence mood at all -- a 2012 meta-analysis of published research found zero correlation between "PMS symptoms" and the actual premenstrual phase of a woman's cycle.
Ekem / Wiki Commons
It's an egg, not a time bomb.
Experts believe that those symptoms may be an expression of the frustration caused by the expectations put on women in Western society. Specifically, the expectation that they be both productive and reproductive members of said society. Women already get tagged with the "hysterical" label if they express emotion in the workplace, so PMS becomes an "express your frustrations for free" card. She didn't call the guy in the next cubicle a dick because she has PMS -- she did it because she does indeed think he's a dick. Saying, or even thinking, that it's the PMS talking is a way to give herself permission to express it.