Here is a short script:

<?php
        $goodday = mktime(0,0,0,10,20,2002);
        $goodsun = strtotime("Sun",$goodday);
        $goodmon = strtotime("Mon",$goodday);
        $gooddif = $goodmon - $goodsun;
        $goodsunstr = date("Ymd.Hi",$goodsun);
        $goodmonstr = date("Ymd.Hi",$goodmon);
 
print "$goodday $gooddif $goodsunstr $goodmonstr <br>\n";
 
        $okday = mktime(0,0,0,10,27,2002);
        $oksun = strtotime("Sun",$okday);
        $badmon = strtotime("Mon",$okday);
        $okdif = $badmon - $oksun;
        $oksunstr = date("Ymd.Hi",$oksun);
        $badmonstr = date("Ymd.Hi",$badmon);
print "$okday $okdif $oksunstr $badmonstr <br>\n";
 
echo "PHP version " . phpversion() . " <br>\n";
 
?>

The output of the script is this:

1035097200 86400 20021020.0000 20021021.0000 
1035702000 86400 20021027.0000 20021027.2300 
PHP version 4.2.3 

Although the difference between Sunday (Oct 27) and Monday is 24 hours, the output from date shows it to be only 23.