Re: Year 2k

Warrl kyree Tale'sedrin (
Fri, 27 Mar 1998 21:01:33 +0000

> From: Arjen Kamphuis <>

> I also read somewhere (but have not been able to confirm it) that the
> GPS-navigation satellites will 'run out of dates' by the end of _this_
> year. It seems their calender is based on counting weeks since 1-1-1980 and
> by next september or something they will run out of memory. Can anyone
> confirm this story?

I haven't heard it, but let's do some credibility analysis.

First analysis: is this way of tracking dates viable? It seems to me
that a GPS satellite would need a great deal higher precision than
this. If they used off-the-shelf date hardware of the sort routinely
used in PCs, then some GPS satellites may have a
year-2000 problem and some won't.

Second analysis: does this way of tracking dates lead to the
predicted effect? For convenience round to 50 weeks per year. A
one-byte week number would provide 5 years; this system, with 1980 as
the base, would run out of dates in late 1984, not 1998. A two-byte
week number would provide nearly 25 years, and run out of dates
sometime in 2004, not 1998. A three- or four-byte week number would
throw the die-off so far out in the future that the satellites will
be replaced before then anyway.

So the story as stated is clearly not credible.

(Caveat: sometimes *reality* is not credible.)

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