How to add month.year column validation

Database contains CHAR(7) type column which must be NOT NULL and must be in 
the format

mm.yyyy

where:

mm - month number, always two digits in range 01 .. 12

. - separator  must be point always.

yyyy - must be four digits in range approx. 1980 .. 2110 .

How to add column validation to table column which forces this ?

Andrus.