Thread: BUG #5031: DATE_TRUNC returns the wrong value when specifying MONTH
The following bug has been logged online:
Bug reference: 5031
Logged by: Mark Douglas
Email address: mark@steelhousemedia.com
PostgreSQL version: 8.4.0
Operating system: Ubunto Linux
Description: DATE_TRUNC returns the wrong value when specifying MONTH
Details:
The following use of DATE_TRUNC returns the wrong value. I called the
function on 2009-09-02. It should return '2009-09-01 00:00:00' for the
following usage:
SELECT DATE_TRUNC('MONTH', CURRENT_DATE);
It instead returns '2009-08-31 17:00:00.
Casting CURRENT_DATE to a TIMESTAMP causes it to return the correct value
but that shouldn't be required. Cast example:
SELECT DATE_TRUNC('MONTH', CAST(CURRENT_DATE AS TIMESTAMP));
"Mark Douglas" <mark@steelhousemedia.com> writes:
> The following use of DATE_TRUNC returns the wrong value. I called the
> function on 2009-09-02. It should return '2009-09-01 00:00:00' for the
> following usage:
> SELECT DATE_TRUNC('MONTH', CURRENT_DATE);
> It instead returns '2009-08-31 17:00:00.
Really? What timezone setting are you using? I get
postgres=# SELECT DATE_TRUNC('MONTH', CURRENT_DATE);
date_trunc
------------------------
2009-09-01 00:00:00-04
(1 row)
with timezone set to 'America/New_York' or equivalent.
This test might also be instructive:
postgres=# select CURRENT_DATE::timestamptz;
timestamptz
------------------------
2009-09-03 00:00:00-04
(1 row)
regards, tom lane
Mark Douglas <mark@steelhousemedia.com> writes:
> I have my timezone set to GMT so there really shouldn't be any time zone adjustments.
Okay ...
postgres=# set timezone = GMT;
SET
postgres=# SELECT DATE_TRUNC('MONTH', CURRENT_DATE);
date_trunc
------------------------
2009-09-01 00:00:00+00
(1 row)
I suspect there's something you're not telling us, like you're
using a client-side library that is doing timezone adjustments
behind your back.
regards, tom lane
I have my timezone set to GMT so there really shouldn't be any time zone ad=
justments.
Mark
On 9/2/09 10:01 PM, "Tom Lane" <tgl@sss.pgh.pa.us> wrote:
"Mark Douglas" <mark@steelhousemedia.com> writes:
> The following use of DATE_TRUNC returns the wrong value. I called the
> function on 2009-09-02. It should return '2009-09-01 00:00:00' for the
> following usage:
> SELECT DATE_TRUNC('MONTH', CURRENT_DATE);
> It instead returns '2009-08-31 17:00:00.
Really? What timezone setting are you using? I get
postgres=3D# SELECT DATE_TRUNC('MONTH', CURRENT_DATE);
date_trunc
------------------------
2009-09-01 00:00:00-04
(1 row)
with timezone set to 'America/New_York' or equivalent.
This test might also be instructive:
postgres=3D# select CURRENT_DATE::timestamptz;
timestamptz
------------------------
2009-09-03 00:00:00-04
(1 row)
regards, tom lane
You're correct. When I run this from psql it returns the correct result. Wh=
en I run it from DBVisualizer, which I normally use, it adjust the result t=
o my local time zone. Thanks for looking into it. Sorry about bugging you w=
ith that.
Thanks,
Mark
On 9/2/09 10:24 PM, "Tom Lane" <tgl@sss.pgh.pa.us> wrote:
Mark Douglas <mark@steelhousemedia.com> writes:
> I have my timezone set to GMT so there really shouldn't be any time zone =
adjustments.
Okay ...
postgres=3D# set timezone =3D GMT;
SET
postgres=3D# SELECT DATE_TRUNC('MONTH', CURRENT_DATE);
date_trunc
------------------------
2009-09-01 00:00:00+00
(1 row)
I suspect there's something you're not telling us, like you're
using a client-side library that is doing timezone adjustments
behind your back.
regards, tom lane