The pill actually takes over control of your cycle, and your period will eventually fall in line with the BROWN pills.
Before that happens you will likely have some break through bleeding during the first pill cycle, which is completely normal.
The pill STOPS your ovulation, thus it chnages when your period is coming.
The period on the pill is not a REAL period, it is simply withdrawal bleeding from lack of hormones. It was added to BC pills to make it more palatable to women in america, and to hopefully make it legal.
Back in the day, BC was illegal..strange huh?