Re: BUG #18518: ::timestamp add minutes and seconds to the converted values - Mailing list pgsql-bugs

On Thu, Jun 20, 2024 at 03:33:29PM +0000, PG Bug reporting form wrote:
> The following bug has been logged on the website:
> 
> Bug reference:      18518
> Logged by:          Nicola Oricchio
> Email address:      nicola.oricchio@vertigis.com
> PostgreSQL version: 12.18
> Operating system:   Ubuntu
> Description:        
> 
> repro:
> create table aaa (dat timestamp without time zone);
> insert into aaa values ('1892-12-31 23:00:00');
> insert into aaa values ('1893-12-31 23:00:00');
> insert into aaa values ('1992-12-31 13:33:12');
> select dat, (dat at time zone 'utc')::timestamp without time zone from aaa
> order by 1;
> 
> output:
>          dat         |      timezone
> ---------------------+---------------------
>  1892-12-31 23:00:00 | 1893-12-31 23:53:28 <-- it should be 1893-01-01
> 00:00:00
>  1893-12-31 23:00:00 | 1894-01-01 00:00:00
>  1992-12-31 13:33:12 | 1992-12-31 14:33:12
> 
> it works correctly with 12.2
>          dat         |      timezone
> ---------------------+---------------------
>  1892-12-31 23:00:00 | 1893-01-01 00:00:00
>  1893-12-31 23:00:00 | 1894-01-01 00:00:00
>  1992-12-31 13:33:12 | 1992-12-31 14:33:12
> 
> time zone is CET

I just ran your test on PG 12.19, and got the right results in the
US/Eastern time zone:

    $ psql test
    psql (12.19)
    Type "help" for help.
    
    test=> SELECT version();
                                              version
    --------------------------------------------------------------------------------------------
     PostgreSQL 12.19 on x86_64-pc-linux-gnu, compiled by gcc (Debian 12.2.0-14) 12.2.0, 64-bit
    (1 row)
    
    create table aaa (dat timestamp without time zone);
    insert into aaa values ('1892-12-31 23:00:00');
    insert into aaa values ('1893-12-31 23:00:00');
    insert into aaa values ('1992-12-31 13:33:12');
    select dat, (dat at time zone 'utc')::timestamp without time zone from aaa
    order by 1;
    
             dat         |      timezone
    ---------------------+---------------------
     1892-12-31 23:00:00 | 1892-12-31 18:00:00
     1893-12-31 23:00:00 | 1893-12-31 18:00:00
     1992-12-31 13:33:12 | 1992-12-31 08:33:12

I am guessing that your time zone database changed in 12.18 as mentioned
in the 12.18 release notes:

    Author: Tom Lane <tgl@sss.pgh.pa.us>
    Branch: master [272a7c303] 2024-02-01 15:57:53 -0500
    Branch: REL_16_STABLE [b4fb76fb5] 2024-02-01 15:57:53 -0500
    Branch: REL_15_STABLE [970b1aeeb] 2024-02-01 15:57:53 -0500
    Branch: REL_14_STABLE [35b8b2c4a] 2024-02-01 15:57:53 -0500
    Branch: REL_13_STABLE [ac3afc3f7] 2024-02-01 15:57:53 -0500
    Branch: REL_12_STABLE [b59ae79b7] 2024-02-01 15:57:53 -0500

          Update time zone data files to <application>tzdata</application>
          release 2024a for DST law changes in Greenland, Kazakhstan, and
          Palestine, plus corrections for the Antarctic stations Casey and
          Vostok.  Also historical corrections for Vietnam, Toronto, and
          Miquelon.

I would look at changes in the $PG_INSTALLDIR/share/timezonesets/ files
for your session timezone value to see the changes that happened between
those two releases.  There are other time zone updates in other 12.*
releases so I don't know which one affected you.  If you download 12.2
and 12.18 and do a diff of $PG_INSTALLDIR/share/timezonesets/ you should
see the changes.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Only you can decide what is important to you.