A warning for FITS y2k implementors

[Peter Bunclark]

Looks suspiciously like truncation rather than rounding, hence
is a bug not a feature...  and of course, if you choose to
read the date but not the time you must surely expect up to 24-hour
quantisation errors?  It's a bit like reading a floating-point value
up to the decimal point and ignoring the rest!

Peter.

Don Wells wrote:
> 
> An implementor of FITS y2k code told me:
> 
>   "..there was one sort of amusing problem with the initial
>   implementation that other systems might run into. By default with the
>   new-style we include the time. But because of floating point rounding,
>   the new style date would turn into previous_day:T23:59:59.99 or
>   whatever. While this is fine for systems that read the time part of
>   the new format, it would presumably cause systems that ignore the time
>   part to think the date was a day earlier than it actually was.."
> 
> -Don [Chair, IAU FITS Working Group]
> --
>   Donald C. Wells         Associate Scientist         dwells at nrao.edu
>                     http://fits.cv.nrao.edu/~dwells
>   National Radio Astronomy Observatory                +1-804-296-0277
>   520 Edgemont Road,   Charlottesville, Virginia       22903-2475 USA