Re: Imprecision of DAYS_PER_MONTH - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: Imprecision of DAYS_PER_MONTH
Date
Msg-id 200507211645.j6LGj6S03544@candle.pha.pa.us
Whole thread Raw
In response to Re: Imprecision of DAYS_PER_MONTH  (Bruno Wolff III <bruno@wolff.to>)
List pgsql-hackers
Bruno Wolff III wrote:
> On Thu, Jul 21, 2005 at 09:39:38 -0400,
>   Bruce Momjian <pgman@candle.pha.pa.us> wrote:
> > 
> > I have added this comment above the DAYS_PER_MONTH macro:
> > 
> >     + /*
> >     +  *    DAYS_PER_MONTH is very imprecise.  The more accurate value is
> >     +  *    365.25/12 = 30.4375, or '30 days 10:30:00'.  Right now we only
> >     +  *    return an integral number of days, but someday perhaps we should
> >     +  *    also return a 'time' value to be used as well.
> >     +  */
> >       #define DAYS_PER_MONTH        30              /* assumes exactly 30 days per month */
> > 
> > Let me add that we could actually do this in many places now because we
> > are already converting to 'time' in those places.  Is this a TODO?
> 
> Shouldn't you be using 365.2425/12 (30.436875) for the number of days per
> month?

OK, comment updated:

/**  DAYS_PER_MONTH is very imprecise.  The more accurate value is*  365.2425/12 = 30.436875, or '30 days 10:29:06'.
Rightnow we only*  return an integral number of days, but someday perhaps we should*  also return a 'time' value to be
usedas well.*/
 


--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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