Comment # 8 on bug 1071763 from Freek de Kruijf

The system does not start anymore on Jan 1st, 1970, but on the date/time of
building the image, however it will start always on that date/time.
A better solution would be to have a start date/time in the boot partition
which is read at boot time. This date/time should regularly be updated when the
system runs and when the system is shutting down.