Not Working.

save_post.php

<?php

function vg_update_timestamp( $post_id ) {

	$startdate = get_post_meta($post_id, 'cmb_from_textdate', true); //not unix timestamp
	$enddate =  get_post_meta($post_id, 'cmb_till_textdate', true);  //not unix timestamp
	
	$timestamp_start = strtotime( $startdate );
	$timestamp_end = strtotime( $enddate );
	
	update_post_meta($post_id, 'cmb_from_textdate_unix', $timestamp_start );	
	update_post_meta($post_id, 'cmb_till_textdate_unix', $timestamp_end );	
}
add_action( 'save_post', 'vg_update_timestamp' );