Command's output definition shouldn't use formatting functions
Formatting functions should be replaced with field type. The function spoils field's information forever. Eg. once datetime is formatted it can't be printed in different format. More flexible approach would be to set field type (to DateTimeField ind this case) and move the formatting logic to output adapters. The adapter then decides how it shoud be formatted. Eg. Json adapter prints more structured info vs. Table adapter tends to shorten things.