Tutorial Step 6: Set Schedule Exceptions
Still in calendar view, choose Work Schedule for Project from the pop-up menu below the resource list, then choose a week in the calendar that appears. You can change the work hours for a specific week, to account for exceptions such as holidays or overtime.
Here Wednesday the 15th is an off-day. To quickly remove working time from the schedule, you can Shift-drag, creating a red box that deletes any working time underneath it. You can see the normal work week's schedule in gray for comparison.