<?php
$previous_date='20101202115755';
$d = strptime($previous_date, '%Y%m%d%H%M%S');
$prev_ts = mktime($d['tm_hour'], $d['tm_min'], $d['tm_sec'], $d['tm_mon'] + 1, $d['tm_mday'], $d['tm_year'] + 1900);
$now = time();
$diff = $now - $prev_ts;
$diff = floor($diff / (60*60*24));
echo 'Difference between ' . date('r', $prev_ts) . ' and ' . date('r', $now) . ': ' . $diff . ' days';