What is considered having a regular period? Does that mean you have to start your period on the same date every month? I'm a little confused

28 days, +/- 28 days from the first day of bleeding until the next first day of bleeding is the textbook answer. Periods that start spontaneously anytime from 26-32 days are normal and can mostly be considered regular. The same day or date each month is not a good defnition, months range from 28-to-31 days in length, rmeber? Good luck!