At 18:19 -0400 30/07/09, Joshua Cranmer wrote:
David Singer wrote:
Against that, one has to realize that "the label of the day before
X" is well-defined for the day before the introduction of the
Gregorian calendar, and iteratively going back to year 1, year 0,
year -1, and so on.
In neither the Gregorian nor the Julian calendars is there a year 0,
as used in conventional speech (formats designed for machine
computation treat the issue a little differently).
Right. I was specifically referring to Proleptic Gregorian Calendar
in the specification ISO 8601, which does. This makes arithmetic
('how many years') and leap calculations ('is X a leap year') simpler.
Wikipedia:
'Mathematically, it is more convenient to include a year zero and
represent earlier years as negative, for the specific purpose of
facilitating the calculation of the number of years between a
negative (BC) year and a positive (AD) year. This is the convention
used in astronomical year numbering and in the international standard
date system, ISO 8601. In these systems, the year 0 is a leap year.
ISO 8601:
NOTE In the proleptic Gregorian calendar, the calendar year [0000] is
a leap year.
--
David Singer
Multimedia Standards, Apple Inc.
