There's plenty of reserved bits in the old protocol to give more bits that the 10 the WN (week number) already has: https://i.imgur.com/QuJDwmb.png https://i.im

There's plenty of reserved bits in the old protocol to give more bits that the 10 the WN (week number) already has: https://i.imgur.com/QuJDwmb.png https://i.imgur.com/QuJDwmb.png Source: Figure 20-1 in https://www.gps.gov/technical/icwg/IS-GPS-200K.pdf https://www.gps.gov/technical/icwg/IS-GPS-200K.pdf Your argument that the space is sparse is true though in the new protocol which has still a message of 300 bytes but no reserved space any more: https://i.imgur.com/xyxCxIi.png https://i.imgur.com/xyxCxIi.png Source: https://www.gps.gov/technical/icwg/IS-GPS-705F.pdf https://www.gps.gov/technical/icwg/IS-GPS-705F.pdf It gives 13 bit to the message at least, making the counters roll over every 157 years instead of every 20. It's still a bit too little IMO. Date counters should either be so short that engineers must design rollovers into the devices (e.g. 1 year) or longer than human lifespans by several orders of magnitude (e.g. 1000 years).