Remember the Y2K bug? It didn't turn out to be the disaster everyone predicted, but come April 6 this year, we could be facing a similar disaster, only this time it's GPS devices rather than computers that may grind to a halt.
As The Register reports, the problem stems from the fact GPS signals include a timestamp and part of the timestamp is a week number stored as ten binary bits. Ten bits allows it to store 1,024 weeks before it resets, which means the reset happens after roughly 20 years. On April 6, that reset happens, potentially causing GPS devices around the world to stop working.
The good news is, existing GPS devices can be patched to avoid this being a problem. However, a patch being available depends on how old your device is and how reliable the company who sold it to you is for issuing software updates. If your device isn't patched, then it will revert to an earlier period of time and GPS positioning will most likely fail.
Any GPS device manufactured after 2010 should be fine as long as it conforms to the ICD-200/IS-GPS-200 specification. Thankfully, we won't have to face this problem again as modern GPS navigation systems including CNAV and MNAV use a 13-bit week number, meaning a reset won't be required before we don't care about GPS anymore, or have all moved to Mars.
For now, if there are some old GPS devices you still rely on, check to see if they can be patched and whether a patch has been released. If one hasn't, and the manufacturer is remaining silent on the subject, don't be surprised if you device starts acting strangely in April.