WWTBAM Bored

Goward explained that GPS works by sending out timing signals. On each satellite, there are multiple atomic clocks. GPS relies on precision timing to operate.

“Essentially, all the GPS satellites are just very, very precise clocks,” said Goward.

In that timing signal, there is a timestamp containing a code. The code is based on the week and seconds in that week when “GPS Time” began or was set. That date started on January 6, 1980.

But since “GPS time” uses only 10-bits to count the weeks and seconds within that week, it can only cover a finite period of time before it runs out of space.

“It turns out it happens roughly every 20 years,” said Parkinson.

That finite period of time is 1,024 weeks or precisely 19.7 years. This period of GPS time called an epoch. When GPS time reaches its finite period, it “rolls over” or resets to zero.

Most modern devices should do just fine. An official at California’s Office of Emergency Services told KPIX 5 that the agency has performed an assessment of various public safety agency radio systems and has worked with the manufacturers of the GPS timing receivers.

In the future, the modernized GPS navigation messages will use 13-bits instead of 10-bits. Experts explain that will push rollovers to roughly every 157 years instead of the current 20.