[Discuss] Unix date beyond 2057

[John Blomfield]

Alan W. Irwin wrote:
> On 2008-02-28 14:25-0800 pw wrote:
>
>> pw wrote:
>>> Hello,
>>>
>>> Does anyone know if there is a patch for
>>> unix date to allow dates beyond 2057?
>>>
>>> Thanks
>>>
>>> Peter
>>
>> Actually that should be 2037 not 2057.
>>
>> The date function doesn't complain about
>> dates beyond 2038 through 2057 but it generates
>> dates that are wrong beyond 01/19/2038.
>
> Yes, on 32-bit Linux boxes time is currently stored as _signed_ 32 bit
> integer number of seconds since epoch (1970 or so) which works out to a
> range of approximately +/- 68 years from the epoch.  However, on 64-bit
> Linux machines, the valid date range grows to +/- 300 billion years!
>
> That is an illustration of Eric Raymond's point that there is no 
> conceivable
> need for machines with word lengths larger than 64 bits so he predicts 
> the
> current transition from 32-bit to 64-bit that is going on is probably the
> last such transition for the human race.  Normally, I pooh-pooh any such
> conclusion about limits for computers because so many have been so wrong
> about that before, but nevertheless, a 128-bit machine would have integer
> ranges that are 2^{64} times larger than a current 64-bit machine, and it
> really is hard to conceive of any practical software application that 
> would
> overflow such a huge integer range.
>
Such a machine is probably of interest to groups involved with the 
mathematical modeling (numerical analysis) of complex physical systems 
e.g. weather forecasting, climate models, aerodynamic fluid flow etc. 
that are essentially solving initial value multi-dimensional 
differential equations, stepping forward into time.  These models suffer 
from rounding errors and the difficulty of predicting the propagation of 
butterfly type events.  In these cases the more precision i.e. the more 
bits per word the better.  Having said that this is normally the realm 
of the big number crunching machines that are probably already 128 bit 
(I'm a bit out of touch these days) and not the PC world.

John Blomfield


> Alan
> __________________________
> Alan W. Irwin
>
> Astronomical research affiliation with Department of Physics and 
> Astronomy,
> University of Victoria (astrowww.phys.uvic.ca).
>
> Programming affiliations with the FreeEOS equation-of-state 
> implementation
> for stellar interiors (freeeos.sf.net); PLplot scientific plotting 
> software
> package (plplot.org); the libLASi project (unifont.org/lasi); the 
> Loads of
> Linux Links project (loll.sf.net); and the Linux Brochure Project
> (lbproject.sf.net).
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