You have been impacted by GPS week rollover in April 2019. Most Garmin devices were ready, however if the unit is impacted then dates started again at the same start date as the previous epoch at August 1999...which would put your date now as December 2000. If you are lucky there may be a firmware update that will fix it, the latest Navigation firmware I can see listed is 4.31.
Edit: Just found this, unfortunately you might be out of luck: [Only registered and activated users can see links. ]
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