Calendar issues

Andrew Paprocki andrew at
Thu Sep 13 06:55:39 PDT 2012

On Thu, Sep 13, 2012 at 12:37 AM, Mark Davis ☕ <mark at> wrote:
>> Anyway, it typically isn't worth the trouble. It is quite customary to use
>> a proleptic calendar; many if not most standards do it.

Having spent a large amount of time dealing with interfacing a
Julian/(British) Gregorian calendar system to ES (complete with
missing days in 1752) and other large codebases to ES which have to
consume the datetimes, proleptic Gregorian is surely the only sane
choice. Calendars are like time zones -- they just change so
infrequently that most people don't consider them as such. But it
doesn't make sense to try to use the interpretation of calendar(s) in
any one country as the reference any more than it does to use EST/EDT
as the basis for times instead of UTC. Like it or not, proleptic
Gregorian is the closest we have to a "universal" calendar for
computers. Even if calendar transitions were not dependent on vantage
point, supporting the Julian/Gregorian hybrid slows date code by
adding conditionals as opposed to being a simple formula.

>>> and Explorer formats it as being in the year 1 BC. Safari calculates the day
>>> according to the Julian calendar, all others use the proleptic Gregorian
>>> calendar.

That is very surprising to me. Can anyone comment on why Safari chose
that implementation?


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