Synchronis time with NMEA GPS

Hi

I use a GPS (GARMIN 1020xs) on my product, for this function http://forum.iqan.se/topic/1063339-backlight-auto-adjuste/ I need to know the real time. By using the NMEA (= Canbus), I can read the GPS time, but it is impossible to change the time of IQAN master.

What do you think about this function ?

PS : there are a time synchronisation with the modem ? (cellular operation give time to a cellphone).

Regards