Hi Edwin,
It is possible to create custom actions in the ATS environment that you can use in your test scripts.
You can find more information about creating custom actions on the following page: https://docs.mendix.com/ATS/refguide-ats-1/custom-actions
BTW there is already a standard ATS Core function that can be used to retrieve the current date, more info: https://docs.mendix.com/ATS/refguide-ats-1/get-current-datetime-string
Good luck, let us know if you worked it out.
Kind regards,
Jeffrey