CFLib.org – Common Function Library Project

Description:
Returns week number of given date based on optional start-of-week day (numeric; in the range of 1 [Sunday] to 7 [Saturday]; defaults to 1). Returns either week number or, if optional third argument was passed (boolean; defaults to false), as week number and year as WW.YYYY

Return Values:
Returns a string (depends on optional argument).

Example:

<cfoutput>
Week number of today's date based on Saturday as first day of week: #customWeekNumber(now(), 7)#<br>
Week number, including year, of today's date based on Monday as first day of week: #customWeekNumber(now(), 2, true)#
</cfoutput>

Parameters:

Full UDF Source:

/**
 * Returns week number based on [optional] custom start of week day
 * 
 * @param date      date to determine week number  (Required)
 * @param weekStart      day of week start (1-7) (Optional)
 * @param returnFormat      boolean to return week number and year instead of just week number (Optional)
 * @return Returns a string (depends on optional argument). 
 * @author Azadi Saryev (azadi.saryev@gmail.com) 
 * @version 0, March 4, 2010 
 */
function customWeekNumber(date) {
    var firstDayOfWeek = 1;
    var theDate = createdate(year(arguments.date), month(arguments.date), day(arguments.date));
    var firstDayOfYear = createdate(year(theDate), 1, 1);
    var firstCustWeekdayOfYear = "";
    var custWeekNum = 0;
    if (arraylen(arguments) gte 2) firstDayOfWeek = arguments[2];
    if (val(firstDayOfWeek) lt 1 OR val(firstDayOfWeek) gt 7) firstDayOfWeek = 1;
    firstCustWeekdayOfYear = dateadd('d', firstDayOfWeek-dayofweek(firstDayOfYear), firstDayOfYear);
    if (datecompare(theDate, firstCustWeekdayOfYear) lt 0) {
        firstDayOfYear = createdate(year(theDate)-1, 1, 1);
        firstCustWeekdayOfYear = dateadd('d', firstDayOfWeek-dayofweek(firstDayOfYear), firstDayOfYear);
    }
    custWeekNum = ceiling(datediff('d', firstCustWeekdayOfYear, theDate)/7);
    if (NOT custWeekNum) custWeekNum = 1;
    if (arraylen(arguments) gte 3 AND arguments[3]) {
        return numberformat(custWeekNum + year(firstCustWeekdayOfYear)/(1 & repeatstring(0, len(year(firstCustWeekdayOfYear)))), '^.' & repeatstring(0, len(year(firstCustWeekdayOfYear)))); //return weeknumber and year as WW.YYYY 
    } else {
        return custWeekNum; //return weeknumber only
    }
}