Both arguments are required.
If either argument is not numeric, the MOD function returns #VALUE!.
With a datetime in A1, the formula below returns the time only:
Detailed explanation here.
Use QUOTIENT to discard the remainder after division.
MOD Function
The Excel MOD function returns the remainder of two numbers after division. For example, MOD(10,3) = 1. The result of MOD carries the same sign as the divisor.
