If you just set it to 'Browser.ExecJS("Date()")' you'll then see why the statement is showing text (for me, it shows 'Wed Oct 07 2015 18:25:03 GMT+0100 (GMT Standard Time)' therefore the last 4 characters are 'ime)')
If the format of the returned date is consistant, then you could try:
mid(Browser.ExecJS("Date()"),11,4)
which for me shows just the yesr.