Savage,
I'm importing from xml using WP All Import plugin also. My xml is a WordPress export of Events+ plugin by Inscub. Similar problem as yours but with a twist...
our xml looks like this
<postmeta>
<meta_key>incsub_event_start</meta_key>
<meta_value>2014-04-20 00:00:00</meta_value>
Could you elaborate on your solution? As per Angelo's suggestion, did you place a function in you theme? If so could you supply it here as an example for me/us. And your import line from WP All Import?