faketime

Fake the system time for a given command. More information: https://manpages.ubuntu.com/manpages/trusty/man1/faketime.1.html.

• 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 any program would act next friday night:

faketime '{{next Friday 1 am}}' {{path/to/any/program}}