05Mar JRC announces measures for GPS Week Number Rollover

Rollover week JRC family

This newsletter contains information in regard to the "GPS week number rollover" and how this affects JRC's GPS receivers and the GPS incorporated equipment.


The GPS system calculates time by counting the number of weeks up to a maximum of 1,023 weeks. After week 1,023, the week number count is reset to zero. This is called “GPS week number rollover”.


The GPS week number rollover occurs every 1,024 weeks which means about once every 19.6 years. Therefore, when 19.6 years have passed from the reference date in the systems, the clock time incorporated in GPS sensors and navigators will be reset, causing as a result errors in display or output of date or unstable occurrence in positioning operation. When GPS week number rollover occurs, our GPS navigator and or sensor may show the following erroneous phenomena:


  1. Date displayed dates back to 19.6 years ago (19 December 1999).
  2. All dated data output by equipment date back to 19.6 years ago.
  3. Due to this inaccurate date, the positioning operation may temporarily become unstable or be interrupted.


JRC announces measures for GPS week number rollover for equipment that is to occur on some of the GPS' on 4th August 2019. The subject models are designed to turn the clock back 19.6 years (December 19, 1999), and will continue to work incorrectly under normal use, however there is no influence on positioning operation.

For details, please see the 2. notice and countermeasures below or click here to download the file.


1. Objective Equipment


Inmarsat C(JUE-75A/75C)

GPS navigator(JLR-7700MKⅡ)

GPS receiver(JLR-4330/4330W/4331/4331W)

GPS compass(JLR-10/10T)

2. Notice and Countermeasures

The rollover day is on the 4th August 2019 at 00:00 AM (UTC).

Equipment Models Subject Serial No. Notice Countermeasures
AIS JHS-180 All Some log date information will
be displayed erroneous. The
erroneous date will be output
to Aux port.
Replace with JHS-183
JHS-182 Up to BB51400*1 Replace with JHS-183
Upgrade the software*5
Inmarsat C JUE-75A/C JUE-75 with optional
GPS kit (6EZSC00031)
Some function of scheduled
calling and position reporting
will operate erroneous.
Connect the external GPS
replace with JUE-87
GPS Navigator JLR-7700MKⅡ Refer JLR-4331 Note that time and date will go back to the starting date (December 19, 1999) when a master-reset of equipment or a battery replacement is carried out after rollover day.

When the time and date
go back to the staring date,
the equipment will return
to normal operation by the
following settings.

Setting method of

Setting method of

Setting method of

Alternatively, replace with the
following equipment respectively:



GPS Receiver JLR-4330 Up to KE54238*2
JLR-4330W All
JLR-4331 Up to KE50478*3
JLR-4331W Up to KE51718*4
GPS Compass JLR-10/10T ALL

*1: Next rollover of BB51401 and after will be August 2025. Notice and countermeasures are same as this.
*2: Next rollover of KE54239 and after will be May 2022. Notice and countermeasures are same as this.
*3: Next rollover of KE50479 and after will be May 2022. Notice and countermeasures are same as this.
*4: Next rollover of KE51719 and after will be May 2022. Notice and countermeasures are same as this.
*5:  For more information, and countermeasures, please contact us. For the software update, the corresponding cost will be charged. It is possible to support in August 2025 with this software to be released.


Please feel feel free to contact us on should you require any additional information or clarification.