Excel already knows when the month ends.
DATEDIF(), which means Date + Dif, is a compatibility function left over from Lotus 1-2-3 that Microsoft adopted in Excel version 2000, which is the only version that explains how this function works.
The Today() function represents the current date in Microsoft Excel. If you type the =Today() function in any cell and press Enter, Excel will show you the current date. Therefore, this method is used ...
Excel’s Date & Time functions ease the workload for bookkeepers, project planners, HR departments, and other jobs where time is money. The four functions covered here—ISOWEEKNUM, WEEKNUM, WORKDAY, ...