Re: How to convert a year+week to a date ?

Hi,

Don't know what you are trying to achieve, but ref. ISO standards week 1 of a given year, is the week where the first thursday is placed. Means that if 1. jan is a friday, week 1 starts on monday 4. jan aso.

Regards, Michael Ringbo

In article <981451696.73827_at_dedale.pandemonium.fr>,   "Deepest Blue" <no_at_where.com> wrote:
> Finally I have written a function to perform this
> before having time to read your response :-(((
>
> The biggest issue was to find the starting date
> of week 1, it must be the first *entire* week
> beggining with a monday.
>
> Here is my code(better with a fixed font...):
>
> drop package pk_util;
> create or replace package pk_util as
> function week2date(param_week in varchar2) /* week is YYYYWW */
> return date; /* returns first day of
 week,
> week 1 will start with 1st monday of year */
> pragma restrict_references(week2date,WNDS,WNPS,RNDS,RNPS);
> end pk_util;
> /
>
> create or replace package body pk_util as
> function week2date(param_week in varchar2)
> return date
> is
> year_str varchar2(4); /* is year of parameter */
> day_number_0101 number; /* of 1st january with 1=sunday to
> 7=saturday */
> week_number number; /* is week of parameter */
> week_start date; /* is the final date computed */
> begin
> year_str := substr(param_week,1,4);
> day_number_0101 := to_char(to_date
 ('0101'||year_str,'DDMMYYYY'),'D');
> week_number := substr(param_week,5,2);
> week_start :=
> to_date(to_char(((week_number-1)*7)+1,'009')||year_str,'DDDYYYY');
> /* ------------------------------------ */
> /* january --days-------------------- */
> /* 1st mo* tu we th fr sa su */
> /* 2nd tu we th fr sa su mo* */
> /* 3rd we th fr sa su mo* th */
> /* 4th th fr sa su mo* tu we */
> /* 5th fr sa su mo* tu we th */
> /* 6th sa su mo* tu we th fr */
> /* 7th su mo* tu we th fr sa */
> /* 8th mo tu we th fr sa su */
> /* 9th th we th fr sa su mo */
> /* 1st day 2 3 4 5 6 7 1 */
> /* 1st mon 1 7 6 5 4 3 2 */
> /* ------------------------------------ */
> if day_number_0101 = 1 then /* sunday */
> return week_start+1;
> end if;
> if day_number_0101 = 2 then /* monday */
> return week_start+0;
> end if;
> if day_number_0101 = 3 then /* tuesday */
> return week_start+6;
> end if;
> if day_number_0101 = 4 then /* wednesday */
> return week_start+5;
> end if;
> if day_number_0101 = 5 then /* thursday */
> return week_start+4;
> end if;
> if day_number_0101 = 6 then /* friday */
> return week_start+3;
> end if;
> if day_number_0101 = 7 then /* saturday */
> return week_start+2;
> end if;
> end week2date;
> end pk_util;
> /
>
>

Sent via Deja.com
http://www.deja.com/ Received on Tue Feb 06 2001 - 04:15:11 CST