Juerd wrote:

I think the problem one has is much bigger even if a day *number* is
ever displayed. Then beginning with 1 because that's where most humans
begin counting, is wrong. It's a technical thing, and that should be
kept as simple as possible, and as technical as possible, for easier
compatibility with existing technical things.

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As a technical remark I like to point out, that you need 8 time points
to define 7 days. Every day is bounded by two such time points---which are
of course 24 hours apart. This is necessary to get the arithmetic right!
Weekday arithmetic is modulo 7. Or put differently
$week.end() - $week.start() == $week.length == 7 days
must hold. If e.g. you start your week with Monday than this becomes
$Sunday.end() - $Monday.start() == 7 days.
The next order of precision in calender arithmetic is the hour *within*
the day, then minutes and seconds. The weeks themselfs are subdivisions
of years. And the scheme is not completely regular in e.g. the Gregorian
calendar---but almost e.g in the Sym454 calendar which only has leap
weeks.
I think, that this type of integer with remainder arithmetic shows up
in Perl6 in other places as well. E.g. chars in strings depending on the
Unicode level and index arithmetic of arrays. Some unification of the
underlying math would be nice, indeed. And that typically involves
starting from 0 and the positive remainder pointing into the day.
Regards,
--
TSa (Thomas Sandlaß)