On 12/7/17, David Simmons <d...@smallscript.com> wrote:
> There are many julian-day website sources, but this one is correct
> present-day all the way back to 4712 B.C. (not including what should be
> 46BC to AD8 leap year anomalies due to early priests LY every 3 year
> error corrections).
> SqLite:
>
> SELECT julianday('0001-01-01 12:00') AS jd
> 1721426correct answer is 1721424
> ---
> SELECT julianday('1582-10-04 12:00') AS jd
> 2299150 correct answer is 2299160There are three separate systems in common use for naming days: (1) The Julian Calendar named after the Caesar (2) The Gregorian Calendar named after a Pope (3) The julian day number, named after some guy named Julius (or maybe it was his father's name that was Julius. Or Julian. I forget...) One confusing aspect of this is even though (1) and (3) have similar names, they are completely unrelated. The ancient world use the Julian calendar. But around 1582, folks began switching over to the Gregorian calendar. This happened slowly over a span of more than 300 years. Several countries (Russia, Turkey) have only switched within living memory. There was a time when, as you traveled about the world, you would not only have to adjust your watch, but you'd also have to adjust your calendar! The conversion from Julian to Gregorian in most English-speaking countries occurred on 1752-09-02 (Julian) which was followed immediately by 1752-09-14 (Gregorian). On your unix system, type "cal 1752" and see that the month of September only had 19 days that year. SQLite does all date computations using the Gregorian calendar. It does this even for dates that predate the invention of the Gregorian calendar. That way it does not have to worry with locale-specific transitions from Julian to Gregorian. The USNO uses the Gregorian calendar for modern dates and the Julian calendar for earlier dates. I do not know what they use as a transition date. The julianday() function of SQLite converts Gregorian calendar dates (type 2) into a julian day number (type 3). The USNO website converts "Calendar dates" (a mixture of Gregorian and Julian dates) into the corresponding Julian day number. These are different computations. SQLite gets the same answer as the USNO as long as the USNO is using the Gregorian calendar. When the USNO switches to the Julian calendar, then the answers diverge. This is not a bug in SQLite's date function. SQLite is computing exactly the correct julian day number given an input gregorian date. That is what the julianday() function in SQLite is defined to do. The date/time functions in SQLite do not know anything about Julian calendar dates. SQLite does not have the capability of converting Julian calendar dates into other systems such as the Gregorian calendar or the julian-day number. -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
