Elapsed time vs work time

Typically, setting a due date requires that you calculate the actual work time required for completion rather than the total time that elapses until the due date.

SLAs, Workflow tasks, and approvals are examples of situations that require the actual work rather than the total time that has elapsed. In this case, only the part of the day when work is performed is considered when determining when the work is to be complete. For example, if a task is due in 10 hours, but the actual time to perform the task is restricted to a business day schedule, the 10 hours of work can only be done at most 8 hours each day. If this work starts at 10am on Monday, it is expected to complete, or be due, on Tuesday at 12pm:
10am-5pm on Monday (6 hours) + 8am-12pm on Tuesday (4 hours)