The Timestamp label has the local substitution parameter {1} that is replaced by the current time in HH:mm:ss format.  If you wish to change the format you can used the [DNN:Date:<format>] substiution variable.  The <format> will accept any valid .Net datetime format string. 

So you can have "As of [DNN:Date:MMM-dd HH:mm]" as the timestamp label and this will produce "As of Jan-30 18:43" 

Hope this helps... /Paul.