The average menstrual cycle lasts 28 days; however, any cycle between 23 and 42 days is typical. Depending on how long yours actually is, you may not have it at the same each month. My cycle is about 30 days, so mine usually comes around the same date, around the eighth to the tenth day each month.
You and me both! I don't have my period at the same time every month, either. Some girls and women have their periods like clockwork, while others have more irregular periods. There really isn't anything that's "typical." 28 days is considered an average length for a menstrual cycle, but it's just an average. Your periods may be closer together or spread a little further apart. Or, like me, your periods might jump all over the calendar. Keep track of your period (first and last day). The next time you visit your healthcare professional you can bring your chart with you and discuss any concerns you have.
Before having my period managed by birth control, the length of time between my periods varied between 25 and 27 days. But it was never like clockwork. Each month was a little different from the next. I also know that the first few years of my period were pretty inconsistent. One thing that really helped me was to keep a calendar (those little pocket ones are great for this) to mark out the days of my cycle. If you start to see major inconsistencies, it would be a good idea to talk to your healthcare professional.