1. Put "Sun" without quotes in a Cell. Let's assume this is in cell A1 here. If you want to generate full names of the day, put "Sunday" without quotes.
Note – The start day can be any day. "Sun" is chosen for illustration purpose only. The start day will be whatever is put in cell A1.
2. Drag the bottom left corner till row 7 (or to any number of rows) by pressing left click. It will automatically generate the names of the week days.
Or
3. Drag the bottom left corner till row 7 (or to any number of rows) by pressing right click.
4. Leave Right Click.
5. From the menu which pops up, select Fill Days .