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.

Whether it’s adding rows or using VLOOKUP, the box is very useful for new and old Excel users alike. 3. New Excel Tip: smart lookup. If you want information from beyond the realms of Excel, another ...

Go to Formulas > Functions Library and select Date & Time > DAY. When the Function Arguments window opens, point to cell A1 or enter A1 in the Serial Number field box. Excel then displays just the ...