<?php
add_filter( 'cron_schedules', 'add_cron_interval' );

function add_cron_interval( $intervals ) {

	/* Add new cron interval */
	$intervals['one_minute'] = array(
		'interval' => 60, /* It's not recomended cron schedules with less then 15 minutes */
		'display'  => esc_html__( 'Every minute' ),
	);

	/* Remove cron interval */
	unset( $intervals['one_minute'] );

	return $intervals;
}