The MONTH() function will returns an integer, 1 thru 12, representing
the month number of a date. In your example, the formula in C4 might
be
=IF(OR(MONTH(B4)=1,MONTH(B4)=3),24,0)

This formula checks the month number of the date in B4, and if it is
either January or March, returns the value 24.

Is this what you're looking for?