Do you remember the year 2000?   The turning of a new millennium.  Do you also remember the concern over whether global computer systems would suddenly stop working?   The concern was over something known as the Y2K (Year 2000) bug.

This bug was due to the way computers handled dates.   Way before the year 2000, programmers didn’t plan for the future and only used two digits to store and process dates.  So, for example, 1990 would be saved as 90, 1992 as 92 etc.   This worked great for years, but how do you then store 2000, or 2001?  This would end up being saved as 00 or 01.

As the year 2000 approached, companies around the world rushed to change programs over to using 4-digit date formats.   As you can imagine, this was a lot of work, as programs dating back to the 80s that were still in use had to be updated.   Going back this far, meant that oftentimes the original programmers were no longer involved in the project making updates even more difficult.

There was uncertainty over whether everything was patched and ready when the New Year came, however a lot of preparation meant that there were no disasters and life went on as usual.

Fast forward to 2019 and we’re approaching another date related bug that could potentially cause problems.   This time the bug is specific to the Global Positioning System – widely known as “GPS”.

The date in question this time is an odd one – April 6th, 2019.

GPS is a system of global satellites that broadcast repetitive messages that earth based devices can receive.   The devices use a method called triangulation which analyses the messages from multiple satellites to determine their location.   GPS is used by all forms of navigation, from cars, to boats, to airplanes, so obviously it’s important that it works perfectly.

When GPS was initially built, it was designed to use a date system that counted weeks with a 10-digit format, with a maximum of 1024 weeks.  This equates to around 19.7 years.

The messages sent from the satellites are timestamped by week, and then seconds in to the week.   The device on the ground uses this timestamp to synchronise the signals and determine its location.

However, on the 6thApril, this 10-digit week format will run out and reset to 0 and here’s where the problem lies.

In 2017 the U.S. Naval Observatory released an FAQ on the problem which warned about the issue.   It stated that the GPS receiver’s month/year conversion could fail and that incorrect time tags could “corrupt navigation data at the system level.”    It mentions that a nanosecond error in GPS time would mean a positioning error of around a foot.   You can imagine what kind of positioning error you’d get from a 19-year time discrepancy!

So how worried should we be?   Not all that worried.   The same problem actually happened on August 21st, 1999 and we didn’t have any problems then.   The difference this year is that we’re a lot more dependent on GPS now than we were then.   I bet you didn’t have a cell phone or car sat nav using GPS back in 1999?

Recently manufactured GPS devices now have a 13-digit week format that will instead last 157 years between resets.   I don’t think I’ll be around to see if we have problems 157 years from now.

So, although I’m not worried about the upcoming April reset, if I had a choice, I’d probably hold off flying until 7thApril, just in case!