One way:

B1: =A1

Format B1 using Format/Cells/Number/Custom dddd


In article .com,
wrote:

I have a spreadsheet that has the date formated to have the day
(Monday) and the date (4/24/05) in one colume (Column A), I also need
a formula that will read this date and only put the day of the week in
the next colume?