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Re: [HACKERS] Date conversion using day of week

From: Brendan Jurd <direvus(at)gmail(dot)com>
To: Adrian Klaver <adrian(dot)klaver(at)gmail(dot)com>
Cc: Steve Crawford <scrawford(at)pinpointresearch(dot)com>, pgsql-general(at)postgresql(dot)org, marc(at)bloodnok(dot)com, hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] Date conversion using day of week
Date: 2011-03-31 16:58:48
Message-ID: AANLkTimf65SmP2fxbsEEK1O4Rxg+6dkEOUiOjCJP86ej@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-generalpgsql-hackers
On 1 April 2011 03:32, Adrian Klaver <adrian(dot)klaver(at)gmail(dot)com> wrote:
> Now I am confused the docs say:
>
> D       day of the week, Sunday(1) to Saturday(7)
> ID      ISO day of the week, Monday(1) to Sunday(7)
>
> This would seem to say they both are one-based but differ on the day that is
> 1.

That's correct for the user-facing interpretation.  Internally,
however, Gregorian day-of-week is represented with Sunday = 0.  I
can't see any good reason in the code for why that should be so, but
it was like that when I found it, and until now I haven't had any
cause to mess with it.

My suggestion for moving forward basically still stands, though.  We'd
need to standardise the use of TmFromChar.d to either one of the
1-based conventions, and convert to the other one as required in
do_to_timestamp.  The Gregorian convention is probably the right
choice for the standard, even though it has the week starting on a
Sunday (ridiculous!) because it means less converting for the majority
of cases.

Cheers,
BJ

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