Perhaps the most important event you’ve never heard of is scheduled to take place on April 6. That’s when the GPS rollover will occur. Without getting too far into the weeds, the Global Positioning System is one of the few but critical mechanisms that supports the accurate measurement of time—by accurate, we mean down to the nanosecond and beyond. This method involves counting weeks, and, every 19 years the week-counter must be reset to zero. This is what will happen on Saturday.