You wake up. Emergency and rescue radios are down. Your location app is offline and planes are grounded worldwide.

The time you see on your phone is synchronized to a clock at the US Naval Observatory, delivered via GPS satellites through your local cell

A Brief History of Time (Synchronization)

We recently got a question: Why pay for timing when the GPS signal is free?

It is well understood that all modern networks and electronics rely on a timing signal from GPS that is not nearly secure or accurate enough

We all rely on GPS for our modern lives. If GPS were to go offline for more than a few hours, the disruptions would spread quickly