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Asked: 2026-05-13T08:56:28+00:00

I’m kind of at a loss here. It seems as though somehow my code

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I’m kind of at a loss here. It seems as though somehow my code is missing a whole week at the end of 2009 and I’ve tried a couple different things.

My base function to get the start and end date for a week is below. Given a Year, Week and Day of the Week it gives you a date.

function datefromweeknr($aYear, $aWeek, $aDay)
    {
        $Days=array('xx','ma','di','wo','do','vr','za','zo');
        //xx = Current Sun, ma = Mon ..... zo = Sun of the next Week
        $DayOfWeek=array_search($aDay,$Days); //get day of week (1=Monday)
        $DayOfWeekRef = date("w", mktime (0,0,0,1,4,$aYear)); //get day of week of January 4 (always week 1)
        if ($DayOfWeekRef==0){
            $DayOfWeekRef=7;
        }
        $ResultDate=mktime(0,0,0,1,4,$aYear)+((($aWeek-1)*7+($DayOfWeek-$DayOfWeekRef))*86400);
        return $ResultDate;
    }

Seemed to work completely fine until I realized that I was missing the week of December 27th 2009 to January 2nd 2010.

echo '<table border="1">';
for($i = 1; $i < 53; $i++){
    if($i < 10){
        $w = '0'.$i.'1';
    }
    else{
        $w = $i.'1';
    }
    echo '<tr><td>Week#'.$i.' </td><td> '.date("Y-m-d",datefromweeknr(2009,$i,"xx")).' </td><td> '.date("Y-m-d",datefromweeknr(2009, $i,"za")).'</td><td> Week = '.date("W: Y-m-d",strtotime("2009W$w")).'  </td></tr>';

}

echo '</table>';

It seems the 52nd week of the year ends on 2009-12-26 and the 1st week of the new year starts on 2010-01-03. I’m losing a whole week, No Bueno!

Anyone know what I’m doing wrong or can point me to a fool proof way of supplying a week number and a year to get me the start and end date of that week without losing any days in the process?

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1 Answer

  1. Editorial Team

    Check here:
    http://www.onlineconversion.com/day_week_number.htm
    If you enter 29 december 2009, so see that US and ISO/Europe give different week numbers (resp. 52 and 53).
    Could this be related to your problem? Which standard do you dates conform too?

    Edit:
    From http://www.epochconverter.com/epoch/weeknumbers.php :
    Week number according to the ISO-8601 standard, weeks starting on Monday. The first week of the year is the week that contains that year’s first Thursday. The highest week number in a year is either 52 or 53.

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