public function get_recurring_payment_due_date_for_scheduler( $next_payment_date = false, $gmt = false ) {

		$date = false === $next_payment_date ? $this->get_next_payment_due_date() : $next_payment_date;

		if ( ! $date ) {
			return new WP_Error( 'invalid-recurring-payment-date', __( 'Next recurring payment due date is not valid', 'lifterlms' ) );
		}
		if ( is_wp_error( $date ) ) {
			return $date;
		}

		// Convert our date to Unix time and UTC before passing to the scheduler.
		// No date parameter passed, or passed date parameter was not in gmt.
		if ( ! $next_payment_date || ( $next_payment_date && ! $gmt ) ) {
			$date = get_gmt_from_date( $date, 'U' );
		} else {
			// Get timestamp.
			$date = date_format( date_create( $date ), 'U' );
		}

		return (int) $date;
	}