I would hope any GPS system would be smart enough to know where the vehicle is since that is the main purpose of GPS. The home button should have no affect on the clock.

GPS satellites use very precise clocks that all have to be exactly synchronized for the system to work. They are set to UTC or Universal Time Coordinated(used to be called GMT). If the clock is consistently off by an hour maybe there would be come confusion regarding time zone or daylight savings time. The GPS time should be 4, 5, or 6 hours ahead of local time (east to west in the US) right now and 5, 6, or 7 hours ahead after Saturday night. The minutes should be right anywhere in the world. If the minutes are off or if you are getting blank display then there certainly sounds like there is a problem.