Skip site navigation (1) Skip section navigation (2)

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

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Leslie S Satenstein <lsatenstein(at)yahoo(dot)com>
Cc: Robert Haas <robertmhaas(at)gmail(dot)com>, Postgres documentation <pgsql-docs(at)postgresql(dot)org>
Subject: Re: Some comments about Julian Dates and possible bug. Please provide feedback.
Date: 2010-12-29 17:56:12
Message-ID: 25438.1293645372@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-docs
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

In response to

pgsql-docs by date

Next:From: Robert HaasDate: 2010-12-30 04:18:23
Subject: Re: Words missing in the following txt
Previous:From: Tom LaneDate: 2010-12-29 17:46:02
Subject: Re: Words missing in the following txt

Privacy Policy | About PostgreSQL
Copyright © 1996-2014 The PostgreSQL Global Development Group