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Calendars (was: Re: leap second)



bruce-1130@debian.novare.net (Bruce Perens)  wrote on 21.06.97 in <m0wffVQ-00J4hTC@golem.pixar.com>:

> Someone wrote:
> > This is completely unacceptable. OS time must be predictable.
>
> Run "cal 9 1752" and tell me that.

Consider it done. And now?

(Besides, isn't that a bug in cal? Not everyone switched in 1752. In fact,  
ISTR that most people switched at other dates - some as late as 1918, I  
think.)

A more serious problem is that the current implementation doesn't allow  
for non-Christian date systems, of which there are several in active use.  
I'd expect that to be a problem for people in both parts of Jerusalem, for  
example.

Does anybody know enough about those other systems to tell if the general  
design would at least work - that is, dates are year/month/day tuples? I  
guess the hour/minute/second convention is pretty much established  
worldwide by now (does anyone know for sure?).

> > Can someone explain to me exactly what POSIX time is?
>
> Posix time includes leap-year-days, but does not include the finer
> resolution of leap-seconds. 21 leap-seconds (number 22 is coming up)
> have been added since New Years Day 1970 to keep clock time in synch
> with astronomical time.

Actually, it probably was a bad idea to use "leap" for both. Leap days are  
fixed by calendar design. Leap seconds are inserted or deleted (both are  
possible) after comparing the atomic clocks to astronomical observations,  
with no predictability at all. Two very different animals.


MfG Kai


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