色々為になったので書き残しておきます。

日付を扱う Calendar class.
http://www.go-pear.org/manual/ja/package.datetime.calendar.php

error_reporting(E_ALL);

require_once('Calendar/Calendar.php');

$start = new Calendar(2001 ,3 ,2);
$end = new Calendar(2002 ,2 ,1);

$year = $start->thisYear();
$month = $start->thisMonth();
$day = $start->thisDay();

$i = 0;

while(sprintf('%04d%02d%02d' ,$year ,$month ,$day) <= sprintf('%04d%02d%02d' ,$end->thisYear() ,$end->thisMonth() ,$end->thisDay())){
	echo($i++ . ':' . $year . '-' . $month . '-' . $day . '<br>');

	$Day = $Day->nextDay('object');
	$year = $Day->thisYear();
	$month = $Day->thisMonth();
	$day = $Day->thisDay();
}

mimic28号でした。