Are you supposed to have your period the same time every month?
Not necessarily. First of all, it may take a while for your body to get things going smoothly and regularly, and your first few periods might not always last the same number of days or come the same number of days apart. You may even skip some months. Most likely your periods and cycles will become more regular as you grow older.
But having a regular period usually means that your periods come roughly the same number of days apart, and last roughly the same number of days. So you can have a regular period that shows up at a different point in each month — for instance, if you have a 22 day cycle, you might get your period towards the end of one month but in the middle of the next.
Some women have irregular periods all their lives, and the number of days of each cycle is different from cycle to cycle.