How to determine final day to give 2 wks notice to landlord

[Jon S.]

Tenant lease converted to month to month so they must give 2 weeks notice. The 1st is the date when rent is due. Today Feb 15th I received notice they are moving out on Feb 28. I’m not sure but is that providing less than 2 weeks notice? The calculation depends whether two weeks is from the first day of the month or the last day the month. Anyone know how it’s calculated? Thank you