Hello!
An easy way to find military time that is more than 12 is to subtract 12 from the number. For example, 14:00-12= 2:00 P.M.
In this case 13-12 is 1:00, and 20-12 is 8:00.
This nurse works from 1:00 P.M. to 8:00 P.M., or the afternoon.
I hope this helps!