"First, it's critical to understand that the term 'workweek,' as defined under the FMLA, is the employee's normal schedule (hours/days per week) prior to the start of FMLA leave.... Second, we apply this normal workweek when calculating how much the FMLA leave the employee has used during the holiday week.... In other words, when making the FMLA calculation, we do not back out the Labor Day holiday from our normal workweek."