Lookup strtotime() and date() functions:
<?php
$fullmontyTime = "20030906132143";
$strYear = substr($fullmontyTime, 0, 8);
$strFullTime = substr($fullmontyTime, 8, 6);
$strHour = substr($strFullTime, 0, 2);
$strMinute = substr($strFullTime, 2,2);
$strSeconds = substr($strFullTime, 4,2);
$validTime = "{$strYear} {$strHour}:{$strMinute}:{$strSeconds}";
if (strtotime($validTime)>1)
{
echo date("d M Y H:i.s",strtotime($validTime));
}
?>