Re: [GENERAL] Getting number of days in a month

[Ken Causey]

Here's my perl implementation:

#######################################
#
#  lastday( month, year (4 digit) )
#
#  Returns: last day of the month
#
#######################################

sub lastday {
   my $month=shift;
   my $year= shift;

   $month--;

   my @days = (31,0,31,30,31,30,31,31,30,31,30,31);

   if($days[$month] != 0){
      return $days[$month];
   } else {
   # It's Feb, test for leap year
      if($year % 4 != 0){
         return 28;
      } elsif($year % 400 == 0){
         return 29;
      } elsif($year % 100 == 0){
         return 28;
      } else {
         return 29;
      }
   } 
}

Ken Causey
ineffable

At 02:26 PM 4/12/00 +0200, you wrote:
>To obtain the number of days in a month, I wrote this function:
>
>CREATE FUNCTION dayCountOfMonth(datetime) RETURNS float AS
>'      DECLARE
>               theDate         ALIAS FOR $1;
>               monthStart      date;
>               monthEnd        date;
>       BEGIN
>               monthStart := DATE_TRUNC(''month'', theDate);
>               monthEnd := monthStart + ''1 month''::timespan - ''1 day''::timespan;
>               RETURN DATE_PART(''doy'', monthEnd) - DATE_PART(''doy'', monthStart) + 
>1;
>       END;
>'      LANGUAGE 'PL/pgSQL';
>
>It seems to work, except with the month of October (10).
>
>dayCountOfMonth('1997-10-1') => 30 
>dayCountOfMonth('1998-10-1') => 30 
>dayCountOfMonth('1999-10-1') => 31
>dayCountOfMonth('2000-10-1') => 30 
>dayCountOfMonth('2001-10-1') => 30
>dayCountOfMonth('2002-10-1') => 30
>dayCountOfMonth('2003-10-1') => 30
>dayCountOfMonth('2004-10-1') => 31
>
>Just one question: WHY??????
>(Note: no trouble with February)
>
>Is there a function that give the number of days of a month?
>
>Thanks,
> 
>Guillaume Perréal - Stagiaire MIAG
>Cemagref (URH), Lyon, France
>Tél: (+33) 4.72.20.87.64
>
>