CFLib.org – Common Function Library Project

Description:
As ISOWeek is to Week(), ISOYear returns the ISOYear of the date input. For 360 days a year, this will be the same as Year(), but from the 29th Dec to 3rd Jan, is may be different. Dates in this range may be part of a week number of a year that differs to the actual year of the date.

Return Values:
Returns a string.

Example:

<cfloop index="x" from="1" to="8">
    <cfset testDate = dateAdd("d",x,"28/Dec/2005")>
    <cfoutput>
        Date: #dateFormat(testDate,"dddd dd/mmm/yyyy")# CF:#year(testDate)# ISO:#ISOYear(testDate)#<br>
    </cfoutput>
</cfloop>

Parameters:

Full UDF Source:

/**
 * Returns the ISO correct year of a given date, necessary for dates from 29th Dec to 3rd Jan.
 * 
 * @param inputDate      The date to format. (Required)
 * @return Returns a string. 
 * @author Pete Gibb (peter.gibb@icaew.co.uk) 
 * @version 1, August 4, 2005 
 */
function ISOYear(inputDate) {
    var inputDay = dayOfWeek(inputDate);
    var yearNo = year(inputDate);
    
    /** If the inputdate IS 29th-31st December, the input year MAY need to be next year **/
    if((dateFormat(inputDate,"ddmm") is "2912" and dayOfWeek(inputDate) eq 2)
    or (dateFormat(inputDate,"ddmm") IS "3012" and listFind("2,3",dayOfWeek(inputDate),",") gt 0)
    or (dateFormat(inputDate,"ddmm") IS "3112" and listFind("2,3,4",dayOfWeek(inputDate),",") gt 0))
    {yearNo=year(inputDate)+1;}
    
    /** If the inputdate IS 1st - 3rd January, the input year MAY need to be previous year **/
    if((dateFormat(inputDate,"ddmm") is "0301" and dayOfWeek(inputDate) eq 1)
    or (dateFormat(inputDate,"ddmm") IS "0201" AND listFind("1,7",dayOfWeek(inputDate),",") gt 0)
    or (dateFormat(inputDate,"ddmm") IS "0101" and listFind("1,7,6",dayOfWeek(inputDate),",") gt 0))
    {yearNo=year(inputDate)-1;}
    
    return yearNo;
}