You would use the text function.
If you have =today()=today()
in A1, you would use =text(A1,"mm/dd/yyyy")=text(A1,"mm/dd/yyyy")
. (There are multiple formats for 'mm/dd/yyyy' if that's not the format you want.)
Alternatively you can pre-format the cell as a date, so pasting the value would automatically be displayed as a date.