GPS “rollover” event on April 6 could have some side-effects

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On April 6, the Global Positioning System will reach the end of an era-or more correctly, an epoch. That's when the Coordinated Universal Time (UTC) clock used by the satellite navigation system will reach the limit for its 10-bit "week number" (WN) counter and flip back to 0000000000.

GPS time is linked to the official UTC clock time provided by the US Naval Observatory. But the GPS version of the clock tracks the date by counting the number of weeks since the beginning of the current GPS "epoch"-August 21, 1999. So as the clock reaches midnight tonight on the prime meridian, the GPS calendar will suddenly become 20 years out of date.

This should not come as a surprise for most newer GPS navigation systems. There has been plenty of warning-GPS went through a similar flip once before. And the Department of Homeland Security's National Cybersecurity & Communications Integration Center issued a warning in April 2018 that this rollover was coming, as it will every 1,024 weeks-until the modernization of the GPS constellation is complete, and then the WN counter will be increased in size to 13 bits.

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