|
|
|
|
|
|
|
8.4.4.3
iso_last_day_of_week () |
|
|
|
|
|
|
|
|
This routine (Listing 8.12) returns the date that is the last day of the week for the given year and week number. The definition of week number follows the ISO rule. This date is always a Sunday. |
|
|
|
|
| Listing 8.12 | |
|
|
|
|
4. This routine uses the 'iso_first_day_of_week ()' routine to perform
the essential validations and calculations, and simply adds 6 to
the date returned by that routine. This strategy avoids duplication
of code and ensures that the routines operate consistently together.
5. The ISO definition of week number depends upon two rules:
5.1. The first day of the week is Monday.
5.2. The first week of the year is the week containing the first
Thursday of the year.
The consequence of these rules is that there are seven cases:
Case 01 JAN Y 1st Thursday Monday starting Sunday ending
Number falls on DOW is date week 1 is date week 1 is date
------ ------------ ------------ --------------- --------------
1 Sunday 05 JAN Y 02 JAN Y 08 JAN Y
2 Monday 04 JAN Y 01 JAN Y 07 JAN Y
3 Tuesday 03 JAN Y 31 DEC Y-1 06 JAN Y
4 Wednesday 02 JAN Y 30 DEC Y-1 05 JAN Y
5 Thursday 01 JAN Y 29 DEC Y-1 04 JAN Y
6 Friday 07 JAN Y 04 JAN Y 10 JAN Y
7 Saturday 06 JAN Y 03 JAN Y 09 JAN Y
*/
#include "scdtl_2.h"
#include "iso_2.h"
struct DATE_INFO iso_last_day_of_week (int year, int week)
{
double jd;
struct DATE_INFO date;
date = iso_first_day_of_week (year, week);
if ( (date.year == 0) && (date.month == 0) && (date.day == 0) )
return (date);
jd = date_to_JD0 (&date);
jd += 6.0;
date = JD0_to_date (jd);
return (date);
}
|
|
|
|
|
|
|
|