Geeetech

I know there's a battery and RTC incorporated in the GSM shield but cannot find any information on how to use it.
GSM is workning fine, and I would really like to use the RTC to time stamp messages.
Any help here would be most appreciated.

I've just started using the GSM shield which seems to work well.
The instructions I have found mention an RTC and buttoncell, but no instructions on how to make use of it.
Can anyone point me in the right direction please.