I have been bemused by the Ewing-Gilmartin debate on date representations. It
recapitulates en petit a good many of the jejune Y2k discussions of the past,
complete with their defenses of the indefensible and their characteristic
crackpot realism.
Perhaps even more seriously, it omits to distinguish between
o internal date formats suitable for computation, and
o external date formats, suitable for display to humans or printing.
External formats vary from culture to culture. Even within the Anglo-American
community 'September 2 1925' is universally intelligible but '2 ix 1925'
astonishres many Americans.
Internal date formats are much simpler and not at all controversial among
coloro che sanno. Choose an epoch origin, the putative birth date of Jesus,
that of the Moslem hegira, Scaliger's -4713 January 1 BCE, whatever; give it
the serial number +1, its predecessor days the serial number 0, -1, -2, . . . ,
and its successor days the serial numbers +2, +3, +4, . . . Whatever your
choice, conversion to someone else's choice is trivial; a single
addition|subtraction suffices.
Using DSNs trivializes calendar arithmetic. Moreover, the conversions
o DSN to <somebody's calendar>
o <somebody's calendar> to DSN
are easy too, although they should be encapsulated in subroutines written by a
calendrical-arithmetic specialist (for the same reasons that a sqrt subroutine
should be written by an approximations specialist). DSNs represented as
signed binary fullword values encompass an interval of 5,879,610 Gregorian
years on both sides of the epoch origin chosen, which is adequate for most
practical purposes, but not for geological or astronomical applications, for
which signed binary doubleword values are required.
Why are these four-byte internal date representations not in wide use?
Everyone who knows enough about calendars and dates to have a right to an
opinion agrees that they should be used exclusively. Why then has this rare
consensus been systematically ignored by the unwashed?
The usual suspects, sloth and ignorance, decisions made by people unqualified
to make them, are, I suppose, sufficient to explain this avoidance of DSNs.
There is probably no need to invoke the resources of that science the Italians
call dietrologia to identify a villain.
John Gilmore Ashland, MA 01721-1817 USA
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