You can (have to) convert the result of the time() function to the format you desire.
There is no built in function for that.
NOTE that MsExcel (probably depending on version) does NOT have a single date system.
What might help is if you take the following transformation:

This adds the number of seconds between 1900-1-1 and 1970-1-1 to the output of time() and divides by the number of seconds in a day. That number can be transferred to excel and when the cell is properly formatted it will show you the (UTC I guess) date and time. Unless you're using a worksheet with 1904 date system.
Success!
Luc