Re: Some comments about Julian Dates and possible bug. Please provide feedback.

Leslie S Satenstein <lsatenstein(at)yahoo(dot)com> writes:
>> I tested and found the algorithm in Postgres to have
>> the day before January 1,0001 calculating as December
>> 31,0000 even though the world calculates the day before
>> January 1,0001 as December 31,-0001.
>
>> 2) Is the algorithm in Postgres correct? I think
>> not, as the calculations for the difference in days between
>> January 1, 0001 and December 31,-0001 is not 367 days, but
>> just the value 1.

This is not a bug, it's just failure to understand the conventions used
internally. If you did the calculations at the SQL level you would get
the right answers:

regression=# select '0001-01-01'::date - 1;
?column?
---------------
0001-12-31 BC
(1 row)

regression=# select '0001-01-01'::date - '0001-12-31 BC'::date;
?column?
----------
1
(1 row)

Internally we represent 1 BC as "year zero", 2 BC as "year -1", etc,
but this isn't a problem from users' perspective.

regards, tom lane