<!-- Collection of code snippets by Arne Vajhøj -->
<!-- posted to eksperten.dk, usenet and other places (2002-now) -->
<?php
function point_rate($t) {
    $parts = getdate($t);
    $wday = $parts['wday'];
    $hours = $parts['hours'];
    if($wday == 0) {
        return 25;
    } else if($wday == 6) {
        return 15;
    } else if($hours >= 18) {
        return 10;
    } else {
        return 5;
    }
}

function hour_fraction($t) {
    $parts = getdate($t);
    $minutes = $parts['minutes'];
    return $minutes / 60;
}

function calc_point($s1, $s2)
{
    $t1 = strtotime($s1);
    $t2 = strtotime($s2);
    $sum = 0;
    $t1x = $t1;
    while($t1x % 3600 != 0) $t1x++;
    $t2x = $t2;
    while($t2x % 3600 != 0) $t2x--;
    for($t = $t1x; $t < $t2x; $t += 3600) {
        $sum += point_rate($t);
    }
    $sum -= hour_fraction($t1) * point_rate($t1);
    $sum += hour_fraction($t2) * point_rate($t2);
    return $sum;
}

echo calc_point('07:00', '19:00') . "\r\n";
echo calc_point('07:30', '19:30') . "\r\n";
echo calc_point('3-Dec-2010 13:00', '3-Dec-2010 15:00') . "\r\n";
echo calc_point('4-Dec-2010 13:00', '4-Dec-2010 15:00') . "\r\n";
echo calc_point('5-Dec-2010 13:00', '5-Dec-2010 15:00') . "\r\n";
echo calc_point('Today 13:00', 'Today 15:00') . "\r\n";
echo calc_point('Tomorrow 13:00', 'Tomorrow 15:00') . "\r\n";
?>