Date – Stringtodate format +1 week etc

";
echo date('Y-m-d', strtotime("10 September 2000")), "
";
echo date('Y-m-d', strtotime("+1 day")), "
";
echo date('d/m/Y', strtotime("+1 week")), "
";
echo date('d/m/Y', strtotime("+1 week 2 days 4 hours 2 seconds")), "
";
echo date('d/m/Y', strtotime("next Thursday")), "
";
echo date('d/m/Y', strtotime("last Monday")), "
";
?>
And date minus 17 years

echo date('d/m/Y', strtotime("-17 years")), "
";

and if that does not work this will (last day of month)
echo $lastDay = date('Y-m-d', mktime(-1, 0, 0, date("m"), 1, date("Y")));
First day of month
echo $firstDay = date('Y-m-d', mktime(+1, 0, 0, date("m"), 1, date("Y")));
OR
echo date('Y-m-d', strtotime('first day of this month'));


+7 days from first day of month
echo $firstDay = date('Y-m-d', mktime(+1, 0, 0, date("m"), 1, date("Y")));
echo "
";
echo $lastday = date('Y-m-d', strtotime('+7 days', strtotime($firstDay)));