Why me

So I was looking at my log and I have 2 period tacking apps 1 said I was gonna have it 3 days ago the other said I'm going to have it tomorrow. Well the only thing that is gonna kill me is the fact that I'm going to San Diego on the 24th meaning I'm going to be on my period at San Diego. Now some of u will be like what's the big deal? The thing is I have only been to California once and I have never visited San Diego and its my first actual trip with my family.