A machine may be available before its operator arrives. Giving the task an earlier working start does not establish that the assigned person is available then. Compare the two calendars as separate constraints on the same interval.

This check uses an automatically scheduled task in Project desktop for Windows. The Task Calendar field identifies its calendar; None uses the project and assigned resource calendars. When a task calendar is applied and resources are assigned, scheduling uses the overlap of task and resource working times. Ignoring resource calendars changes that rule.

Write down the overlap before editing

In a disposable plan, suppose the task allows 08:00–12:00 and its one resource allows 10:00–16:00 on the same day, with no breaks or exceptions. Their overlap is 10:00–12:00: two hours. A two-hour task can fit that window; a three-hour requirement cannot fit wholly within it.

To define a test task calendar, use Project, Change Working Time, Create New Calendar. Give the copy a distinctive name. Under Work Weeks, Details, set the selected days' working intervals. Apply it through the task's Information, Advanced, Calendar selection. Keep the resource calendar as a separate input to inspect.

Now extend only the task window to 07:00–12:00. Its own allowance increases from four to five hours, but the common interval remains two hours. Extending the task finish to 13:00 instead would make the common interval three hours under these stated assumptions.

Check which restriction would be overridden

The Advanced option Scheduling ignores resource calendars lets the task calendar control scheduling despite resource nonworking time. Microsoft explicitly warns that this can schedule work when the resource is unavailable. Treat the checkbox as a change of assumption, not a routine repair for an inconvenient finish date.

For the actual plan, obtain the intended hours from the responsible people before changing either calendar. Record exceptions, breaks and the relevant date; two calendars with similar names can have different working intervals that week.

Compare the scheduled time with the written overlap and investigate any discrepancy alongside task mode and other constraints. Acceptance means the task fits the declared availability, or an authorised exception is clearly documented. A longer task calendar by itself is not evidence of extra staffing capacity.

Sources: Microsoft: task calendar field; Microsoft: supporting procedure.