What is GPS Week Number Rollover and how to reset incorrect date from GPS?

GPS Week Number Rollover occurs every 1,024 weeks (19.6 years). When the GPS satellite system's week counter reaches its limit of 1,023, an integer overflow causes the internal value to reset to zero and start counting again. The last time this happened was on April 6, 2019.

All GPS receivers use this week counter to calculate the current UTC date. Therefore, the date of launch/manufacture of the GPS chipset built into the GPS receiver will determine when the GPS will reset. (Launch date + 19.7 years = reset date). This will, in turn, determine the date error displayed.

For example, a GPS unit manufactured in 2003 will reset and restart in 2023 after 19.7 years have passed. Practically, this means that your system will start displaying the date as 2003 at some point in 2023.

Raymarine is pleased to announce that none of the current products that include a GPS receiver are affected by the upcoming GPS week counter reset in April 2019. This includes Axiom 2 & Axiom MFDs, Element, Dragonfly, RS150, and AR200. Discontinued products such as a/c/e/eS/gS MFDs, RS130, RAY52-70 are also not affected.

Through our review of Raymarine products, some early older products will have date-related performance issues now and in the future. The table below provides an approximate indication of the reset date and any corrective actions required. Note that GPS receivers affected by this can still generate a valid position fix and SOG/COG but display the wrong date. This will affect the accuracy of chart functions such as tides and currents due to the date being reset by 1,024 weeks from the reset date. Products connected to a GPS receiver using the date for certain functions must also be checked.

If you have a GPS product affected by the week number reset, the following actions should be considered:

• Check the list below for GPS products affected.
• Check the accuracy of the position fix. If it is incorrect, this can be reset by cold-starting the GPS.
• If the position fix does not reset, the GPS may have a real fault and not related to the reset.
• GPS receivers affected and used in a system that needs the correct date should be replaced.

The table below includes current and older Raymarine GPS antennas and products with built-in GPS receivers and provides an approximate indication of the week number reset and any corrective actions required.