Would it come at the same time next month?

This month my period is late it usually comes in the early 20's although not perfectly regular but when it does come if i were to start taking the pill would that make my next one exactly the same time next month..? It is just that I really do not want it in the start of September as I have to go on this camping thing and I thought it would be fine until now when it has not come yet and is late is there anyway I can avoid getting it at the start of September?