faketime

Fake the system time for a command. More information: https://manned.org/faketime.

• Fake the time to this evening, before printing the result of date:

faketime 'today 23:30' date

• Open a new Bash shell, which uses yesterday as the current date:

faketime 'yesterday' bash

• Simulate how a program would act next Friday night:

faketime 'next Friday 1 am' path/to/program