Mid Month 30 day notice on month to month

[Cory Campbell]

I have a tenant currently in a month to month agreement that gave me 30 day notice in the middle of the month (15th) and they would ideally like to move out in the middle of next month (15th), is it appropriate to allow this and prorate that last month or have it operate by the true beginning and end of the month? I have looked through my rental agreement and it's not black and white in there. Any thoughts or guidance would be great. Thank you