The females heat cycle is about 12 days,I'm pretty sure. And the bleeding part is no fun.
You DO NOT want to wear any white clothing becasue if her rear touches you there will be a few red smears. One female I had bled so much that it looked like a murder-masacer in the house,it was on the walls even! That was just to much for me, I put her butt in her kennel and let her stay there until it was over.
And all of the males go crazy,they go into what I like to call the "Mad Humpind Disease". You can't sit down without a dog attached to your leg. I swear it's the worst time for me,I'm the one needing the midol not the dog..lol.
Anyway thats just a brief discription.