Semantics? February has 28/29 days. How does 30 Day Notice work?

[Mindy Jensen]

A question about a 30 Day Notice for a Month to Month tenancy brought up a question. This year, February has 29 days, but 75% of the time only has 28 days. Does a 30-Day notice on January 31 mean tenancy ends at the end of February, or are you obligated to wait until the end of March due to the calendar?

Obviously you can just plan ahead to make sure you're giving 30 actual days notice, but I'm wondering if, in some of the more tenant-friendly states, this messes you up?