For the month of Feb with 28 days, is notice on the 14th enough days?

Today is the 7th. Why not earlier if you need 15 days? I believe it is "At least 15 days"

Assuming this is Florida (it helps to specify), the 15 day notice must be prior to the end of the rental period. To be safe I would deliver the notice before the 12th.

"[Florida Statute] 83.03 Termination of tenancy at will; length of notice.—A tenancy at will may be terminated by either party giving notice as follows:
(1) Where the tenancy is from year to year, by giving not less than 3 months' notice prior to the end of any annual period;
(2) Where the tenancy is from quarter to quarter, by giving not less than 45 days' notice prior to the end of any quarter;
(3) Where the tenancy is from month to month, by giving not less than 15 days' notice prior to the end of any monthly period; and
(4) Where the tenancy is from week to week, by giving not less than 7 days' notice prior to the end of any weekly period." (emphasis added)

So, as ScottGem has indicated, the notice must be 15 days "prior to the end of" the period. I don't see that OP has indicated when the period starts and ends. If, for example, if the tenant started paying rent in the middle of a month, it's arguable that the "rental period" would begin on the 16th of each month and end on the 15th of the next month.

I'm assuming since the OP indicated a calendar month, that the rental period ends at the end of the month. If the OP is a landlord and plans on giving a termination notice, I would do it Monday. The deadline for the tenant to vacate would be the end of the rental period, presumably the 28th. If the notice is not delivered at least 15 days prior to the end of the rental period then the tenant will have another rental period before they have to vacate.

I agree with Scott, 14 days is not 15 days,