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Re: Inconsistant DOW...

From: Patrick Welche <prlw1(at)newn(dot)cam(dot)ac(dot)uk>
To: "W(dot)B(dot)Hill" <bill(at)hillzaa1(dot)miniserver(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Inconsistant DOW...
Date: 2004-06-28 17:02:01
Message-ID: 20040628170201.GJ550@quartz.newn.cam.ac.uk (view raw or flat)
Thread:
Lists: pgsql-general
On Mon, Jun 28, 2004 at 04:23:25PM +0000, W.B.Hill wrote:
> Hiya!
> 
> What's happening, where've I goofed?
> 
> CREATE TABLE test (d date);

Try using

  CREATE TABLE test (d timestamp without timezone);

instead..

> SELECT d+'45 days ago'::interval FROM test;
>         ?column?
> ------------------------
>  2004-02-25 23:00:00+00
>  2005-02-10 00:00:00+00
>  2006-03-01 23:00:00+00
>  2007-02-21 23:00:00+00
>  2008-02-07 00:00:00+00
>  2009-02-25 23:00:00+00
>  2010-02-17 23:00:00+00
> (7 rows)
> 
> Why the different times??? Why the times???

Different times because of summer time starting before or after Ash
Wednesday, times because of implicit type casting - what is the
type of date + interval ?

> SELECT date_part('dow',d+'45 days ago'::interval) FROM test;
>  date_part
> -----------
>          3
>          4
>          3
>          3
>          4
>          3
>          3
> (7 rows)
> 
> So, Ash Wednesday's on a Thursday iff Easter's in March???
> Hmmm.

I'd try adding 46 days ago ;)

Cheers,

Patrick

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