try this
$date = '2014-03-13T09:05:50.240Z';
$fixed = date('Y-m-d', strtotime($date));
The complete date function documentation can be found here: http://php.net/manual/en/function.date.php
The PHP function "strtotime" does nothing else then converting your timestring into an unix timestamp.
Hope I could help :)
P.s.:
Just in case strtotime will return 0 try using this:
$date = '2014-03-13T09:05:50.240Z';
$fixed = date('Y-m-d', strtotime(substr($date,0,10)));
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