What problem are you trying to solve with Submitty
Currently upload/download gradeable json file functionality lacks testing for date values.

Describe the way you'd like to solve this problem
Adding tests for these values will ensure the code functions well and any errors can be caught properly.

Describe any potential alternatives you'd tried to solve the problem
#12699 adds testing for has_release_date value. There are still other date values that can benefit from testing.