A GPS signal contains three different bits of information - a pseudorandom code, ephemeris data and almanac data. The pseudorandom code is simply an I.D. code that identifies which satellite is transmitting information. You can view this number on your Garmin GPS unit's satellite page, as it identifies which satellites it's receiving.Ephemeris data, which is constantly transmitted by each satellite, contains important information about the status of the satellite (healthy or unhealthy), current date and time. This part of the signal is essential for determining a position.The almanac data tells the GPS receiver where each GPS satellite should be at any time throughout the day. Each satellite transmits almanac data showing the orbital information for that satellite and for every other satellite in the system.
I agree GPS may not track DST directly, but if it doesn't incorporate a DST adjustment, I would still expect the Navigon to be able to get the base time from the GPS and adjust according to timezone/DST.
In the options menu GPS status (or if you click with other versions on the satellite symbol) the information about the GPS receiption is displayed for you:GMT (Greenwich Mean Time):Mean solar time in the prime meridian. This time represents the relation between the displayed time and the calculation of the actual time and a possible arrival time. The actual time (time zones, summer time winter time) are taken from the map material data.