query

// WP_Query arguments
$args = array(
	'post_type'              => array( 'publicaciones' ),
	'post_status'            => array( 'publish' ),
	'nopaging'               => true,
	'meta_query'             => array(
		'relation' => 'AND',
		array(
			'key'     => 'fecha_de_inicio',
			'value'   => '$date_now',
			'compare' => '<=',
			'type'    => 'DATE',
		),
		array(
			'key'     => 'fecha_de_fin',
			'value'   => '$date_now',
			'compare' => '>=',
			'type'    => 'DATE',
		),
	),
);

// The Query
$query = new WP_Query( $args );