Masaki Kouda <fp6m-kud@...> wrote:

>
> Pierre Laporte <laportepierre@...> wrote:
>>An other "useless" addition�.
>>
>>Guide is smart enough to advise us about using the wrong calendar
>>(Julian or Gregorian)according to the year selected. Recently, I was
>>using Guide as an "historical tool" to get the day of the week birthday
>>of J.S. Bach on 21 march 1685. I got the wrong answer because Eisnach
>>(birthplace of Bach) is in Germany and that country adopted the
>>Gregorian calendar only in 1701. Guide manual instructs us for the
>>year for some other exceptional countries. Is it feasible to let Guide
>>smart enough to change this warning according to the country of the
>>location identify by Guide. So German or Russian users won't have to
>>bother about remembering when they are using the Julian or the
>>Gregorian calendar
>
> This feature looks nice. But it make us in confusion probably.
> For example, Japanese use Chinese-like calendar until 1872.
> 1873-1899 Japanese use Julian Calendar (!)
> 1900-current Japanese use Gregorian Calendar.
>
> I know this is very spacial case. And I think some country
> doesn't use Gregorian calender yet.

To have Guide automatically select the calendar in use at a specific
time and location will easily become a can of worms. The transition
from Julian to Gregorian calendar was particularly chaotic in
Germany, where the Catholic parts switched early, while the
Protestant parts switched later. There were even disagreements
within some CITIES about this, which means some parts of the same
city could use the Julian calendar while another part used the
Gregorian calendar.

There were also special cases. One special canse occurred in my own
country, Sweden: from 1700 to 1712 Sweden used a celandar which was
one day ahead of the Julian calendar. The original idea was to skip
all leap days from 1700 to 1740, in order to "gradually" switch from
Julian to Gregorian calendar. So we skipped the leap day in 1700 and
was one day ahead of the Julian calendar. However, the Swedish
government wasy busy with various wars/etc, and forgot about this, so
in 1704 and 1708 the leap days weren't skipped. In 1712 we were
still one day ahead of the Julian calendar, so we decided to go back
to the Julian calendar by adding TWO leap days to Febr 1712: thus, in
Sweden in 1712, February had 30 days! From 1712 we remained on the
Julian calendar until 1753, when we finally switched to the Gregorian
calendar by skipping the last 11 days of February.

It is unreaonable to expect Guide to properly handle all these
special cases. In some cases it's even unclear when some specific
region switched from Julian to Gregorian: different sources give
somewhat different dates, and we're unable to determine which source
is right.

Finally: before the introduction of the Gregorian calendar, many
places used a different date for new year than 1 Jan. The Vernal
Equinox was a popular alternative New Year's date, but other dates
were used as well. Should Guide account for this too? No, that's
not a reasonable requirement I think.

----------------------------------------------------------------
Paul Schlyter, Swedish Amateur Astronomer's Society (SAAF)
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