<?php
$re = "/^((?:\\d{2}\\.?){3}).+(\\D{1}\\d{1}\\s\\d{4})/";
$str = "A N K U N F T 11.08.15\n*** N ***\n11.08.15 xxx xxx X3 2830 14:25 17:50\n18.08.15 xxx xxx X3 2830 18:40 F882129 dsdsaidsaia F882129 xxxyxyagydaysd";
$subst = "--";
preg_match_all($re, $str, $matches);
print_r($matches);
?>