GM and Denso tried to help with this one, but they were able to release the update CD only for some specific makes and models. Unfortunately, Denso does not already have the source codes for software in SAAB GPS navigation units, after all those years, they will not be able to release the update for us all.
However, there is some minor possibility, it would start working back by itself in August of 2020, as GPS clock format might be recognized by the original version of software.
Some people already got it fixed by accident, when their GPS simply received broken signal that was translated in some time / date to the navigation unit. Other possibility is to use a fake GPS signal generator, emitting the time / date of the past, which would again work only until battery is unplugged again.
The most suffering are the 2006+ “Dame Edna” facelift owners, where navigation is the only inner source of current time and date, which is also used for service intervals and for the programmable heater. for those who are not familiar with the term “Dame Edna” – it was used in reference to the front end of the 06-09 Saab 9-5 with the chrome surrounds.