Every 20 years there is a date roll over for GPS chartplotters due to early software limitations and the Way a date was stored. The last time this happened was on August 21st, 1999. If you are still using a GPS that was built last century, you may find that you could experience some difficulties.

What is the GPS 2019 Week 1024 Rollover?

The Global Positioning System (GPS) provides very accurate timing which is transmitted to our GPS Receivers from the GPS satellites. This is used to calculate position fixes, and to display the date and time on the GPS CDU’s.

The timing information includes the ability to transmit the Current week, and number of seconds into that week. The GPS Receiver translates this into a more common format of time of day, day, month and year. The weeks are represented by a 10-bit binary number, which limits the Range of the week number to 1024 weeks, with the counter reset to zero at the completion of week 1023.

GPS week zero started on January 6 1980, and the 1023 week counter rolled over on August 21, 1999 with the week counter reset to zero on August 22, 1999. The next one is the 6th April 2019.

Some older GPS receivers are unable to make the transition from week 1023 back to week zero. If your GPS Receiver is outdated or has not had a software update, it may revert to reading the week zero as August 1999. When this happens, the internal clocks of these GPS receivers will experience a lack of absolute reference and may give incorrect time or position information, or may lock up permanently. Some GPS receivers may experience issues and disruptions prior to or after the rollover date.

Issues could occur if:

• Receivers have been in operation for more than 10-15 years without firmware updates.
• Receivers are part of a critical timing system, i.e. what would be the impact to the system if the GPS Receiver starts to output incorrect >UTC data?

As with most issues like this, we recommend that you make sure you are using the manufacturer's latest software, as potential problems like these are resolved, sometimes without specifically mentioning it. So if in doubt, update!
 

Furuno had an earlier date than most other brands - 17 March. A List of affected units can be found here.

Raymarine posted advice about their models here.

Garmin believes most of their units will be unaffected (read more here).

Lowrance expect some units to be affected - check here (read more here)

Simrad expect some units to be affected - check here (read more here)

B&G expect some units to be affected - check here (read more here)

Humminbird have advised that GPS displays were all manufactured after 2000 and conclude that therefore they are unaffected.

For further information on all things GPS-related, you can get in touch with us at CH Smith Marine on (03) 9403 4800.