The GPS system is mainly based on very acurate atomic clocks installed in the GPS satellites. The carNAVi is receiving this time signal during position determination. Depending on the status of the unit - for example how long it was switched off, or moved over a long distance - it may take some minutes to receive the correct position of the satellites and also the time and date.

The carNAVi doesn't have a battery buffered real time clock, mainly because the battery will not drain if the unit is switched off, so it needs to receive the time always after a cold start (switching on).

The positive effect of this is, that the unit can be switched off for a very long time, and the battery still has charge, because a switched off carNAVi consumes absolutely no energy.