DATEDIF(), which means Date + Dif, is a compatibility function left over from Lotus 1-2-3 that Microsoft adopted in Excel version 2000. It's fallen off current Excel menus, but you can still use it.

Press "Ctrl-V" to paste the start and end times for the first work day into these currently empty cells. Excel will automatically adjust the formula cell references for each day of the work week.

To do so, use an Excel formula taking the difference between the two cells containing times. For instance, if the time the employee clocked in is in cell A2 and the time the employee clocked out ...

From Formulas > Function, select Date & Time, then select DAYS from the drop list. In the End_Date field box, point to A4, and in the Start_Date field box, point to A5. Or just move your cursor to ...