Have you tried putting in text like

"Report updated " & TODAY()

and it comes up with a number –

Report updated 39828

The solution is TEXT function:

="Report updated "&TEXT(TODAY(),"MMMM YY") 

which will result in

Report updated January 09

TEXT needs two arguments –

1.    The number or date – you can use TODAY() or a cell reference

2.    A date/time 'picture' - dd mmm yyyy