From http://www.ez.no/ez_publish/documentation/development/libraries/ez_template/operators/miscellaneous
If you need to access the date of a "ezdate" attribute, you must use
{$node.object.data_map.datum.data_int} to get the unix timestamp ("datum" is the attribute identifier)
Of course, you don't want to print the timestamp, so do something like this:
{$node.object.data_map.datum.data_int|l10n(shortdate)} to get a nice, localized daten print