Mega Code Archive
Count how many weeks in the month have a specified day
<![CDATA[
<?
//
// count how many weeks in the month have a specified day, such as Monday.
// we know there will be 4 or 5, so no need to check for $weeks<4 or $weeks>5
//
// Initial formula doesn't work well, so I "reversed-engineered" to get the formula.
// 0 - Sunday,...,6 - Saturday
for ($year = 2001; $year <= 2037; $year++)
{
for ($month = 1; $month <= 12; $month++)
{
$num_of_days = date("t", mktime(0,0,0,$month,1,$year));
echo "<HR> Month=$month Year=$year <BR>";
echo "Number of days = $num_of_days <BR>";
$firstdayname = date("D", mktime(0, 0, 0, $month, 1, $year));
$firstday = date("w", mktime(0, 0, 0, $month, 1, $year));
$lastday = date("t", mktime(0, 0, 0, $month, 1, $year));
echo "First day of the month = $firstday,$firstdayname <BR> ";
for ($day_of_week = 0; $day_of_week <= 6; $day_of_week++)
{
if ($firstday > $day_of_week) {
// means we need to jump to the second week to find the first $day_of_week
$d = (7 - ($firstday - $day_of_week)) + 1;
} elseif ($firstday < $day_of_week) {
// correct week, now move forward to specified day
$d = ($day_of_week - $firstday + 1);
} else {
// my "reversed-engineered" formula
if ($lastday==28) // max of 4 occurences each in the month of February with
28
days
$d = ($firstday + 4);
elseif ($firstday==4)
$d = ($firstday - 2);
elseif ($firstday==5 )
$d = ($firstday - 3);
elseif ($firstday==6)
$d = ($firstday - 4);
else
$d = ($firstday - 1);
if ($lastday==29) // only 1 set of 5 occurences each in the month of
February with
29 days
$d -= 1;
}
$d += 28; // jump to the 5th week and see if the day exists
if ($d > $lastday) {
$weeks = 4;
} else {
$weeks = 5;
}
if ($day_of_week==0) echo "Sun ";
elseif ($day_of_week==1) echo "Mon ";
elseif ($day_of_week==2) echo "Tue ";
elseif ($day_of_week==3) echo "Wed ";
elseif ($day_of_week==4) echo "Thu ";
elseif ($day_of_week==5) echo "Fri ";
else echo "Sat ";
echo "occurences = $weeks <BR> ";
} // for $day_of_week loop
} // for $mth loop
} // for $year loop
?>
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