First off this might note be the best forum to post this in but I'm looking for an answer better than anything SG can give.

I heard that if a group of women begin to live together, their menstration cycle happens at the same time.

Eg. Five women move into the same house, all of them having diffrent times of menstration. After some time, all the Women get their periods at the same time.

Is this true? How does the female body become intune with the other females?

Their evil powers.

Yes, it's true. I've experienced it. But I haven't found a definitive answer as to why this happens. Most likely it has something to do with hormones and pheromones.

Cecil Adam's comment on this. (http://www.straightdope.com/classics/a2_306.html)

As he suggests, it's also true that my cycle has been influenced (usually, become more regular) with consistent male company.

Wow...I thought it was an urban myth!

lol jk (im not that incompetent)