I have a question on why don't my period come when it's suppose too? I use a calendar on my phone that tells me when my period is coming and when I'm Ovulating. The dates that the calendar give me, aren't the days I come on my period. I sometimes come a day late or a week later.

There is very little that is regular or normal when it comes to menstruation and ovulation.
What you see are AVERAGES of millions of women. The range can be huge for each woman.

Your body has its own cycle, and the apps used on phones and such have a general period cycle that is follows, usually 28 days. And some women just have irregular cycles, meaning that won't happen every set amount of days between periods for the woman like some do. Sometimes you can go on the settings and change the date to fit your last few cycles, or you can manually count to get a better estimate on when you will start.

So having unprotected sex can't change anything?

You will obviously get pregnant eventually when you do that of course, but as far as changing your regular cycle - no. Having unprotected sex will only change that when you become pregnant, in which case you will normally not have a period at all. But please be smart enough to protect yourself and have protected sex.