Garmin GPS Week Number Rollover Statement

What is the GPS Week Number Rollover (WNRO)?

The GPS system is world-renowned for its ability to provide accurate and reliable positioning and timing information worldwide. The GPS satellites transmit to users the date and time accurate to nanoseconds. However, back in 1980, when the GPS system first began to keep track of time, the date and time were represented by a counter that could only count forward to a maximum of 1024 weeks, or about 19.7 years. After 1024 weeks had elapsed, this counter “rolled over” to zero, and GPS time started counting forward again. This first rollover occurred in August of 1999. The second rollover occurred on April 6, 2019.

Is My Device Affected?

For many years, Garmin has anticipated and prepared for this event. Garmin has performed exhaustive testing of current and legacy devices to determine if they would be affected by the GPS week number rollover. Our testing shows the vast majority of Garmin GPS devices have handled the WNRO without issues. Some devices may require a software update. For more information on installing software updates, see - Help with Product Updates.

What is the Effect of a GPS Week Number Rollover Issue?

For GPS devices that are affected, after the rollover occurs, an incorrect date and time will be displayed. This incorrect time will also be used to timestamp track logs, compute sunrise and sunset, and other functions that rely upon the correct date and time. However, barring noted exceptions below, the position accuracy will not be effected and the device will deliver the same positioning performance as before the rollover.

An issue related to erroneous position reporting was reported for the Garmin AIS 600, which was corrected via a Software Update in 2019. For more information, see - AIS 600 Sending Incorrect Position.