Re: Inconsistant DOW...

W.B.Hill wrote:
> Hiya!
> 
> What's happening, where've I goofed?
> 
> CREATE TABLE test (d date);
[snip]
> 
> This is good - every Easter's on a Sunday so far...
> 
> 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???

At a guess, the date is being converted into a timestamp with timezone 
so you can add the interval to it. At another guess, the 1hr difference 
is due to the effects of daylight-savings-time (or whatever it's called 
in your locale).

I've got a feeling '45 days'==45*'24 hours' which, going over a DST 
boundary isn't true for one day. Simplest solution would probably be to 
add a few hours to the date before doing your calculations and then 
casting back to a date.

--
   Richard Huxton
   Archonet Ltd