I wrote:
>> Perhaps it'd be worth documenting that you can get the standard
>> astronomical definition of Julian date by transposing to time zone UTC-12
>> before converting.
BTW ... I'd first thought that the way to do this was to rotate to
time zone UTC+12. I convinced myself on two separate days that UTC-12
was correct instead, but now I'm thinking I was right the first time.
In particular, the results I'm getting with UTC-12 don't square with
the example on Wikipedia [1], which says "the Julian Date for
00:30:00.0 UT January 1, 2013, is 2 456 293.520 833":
regression=# select extract(julian from '2013-01-01 00:30+00'::timestamptz at time zone 'utc-12');
extract
------------------------------
2456294.52083333333333333333
(1 row)
But using UTC+12 does match:
regression=# select extract(julian from '2013-01-01 00:30+00'::timestamptz at time zone 'utc+12');
extract
------------------------------
2456293.52083333333333333333
(1 row)
Of course Wikipedia has been known to contain errors, but now
I'm inclined to think I blew this. Anyone want to check my work?
regards, tom lane
[1] https://en.wikipedia.org/wiki/Julian_day
