This is the first note that I have submitted to php.net:

This function convert a data from W3C to RFC 2822 format. Only one row, but seems it works!

W3C format: http://www.w3.org/TR/NOTE-datetime
RFC 2822 format: http://www.ietf.org/rfc/rfc2822.txt

<?php
// Convert a date from W3C ro RFC 2822 format
function convertDateW3CtoRFC2822($dateW3C) {

return date('r',strtotime(str_replace("+"," +",
str_replace("T"," ",
ereg_replace("([+].*):”,”\1″,$dateW3C)))));
}
?>