Assign a Task Due Date by the Hours Not Days

We are new to the world of task assignment.

Is it possible to assign a length of time the task should be completed in hours, not by the number of days?

We have some SLA's in place on our sales team that instruct follow up in say 4 hours versus 3 days.  When I drag the assign task workflow over, the only option appears to be days.

Does anyone have any recommendations on how to overcome this?

Thank you,

Christine