Source

File: wp-includes/customize/class-wp-customize-date-time-control.php

public function json() {
		$data = parent::json();

		$data['maxYear']          = intval( $this->max_year );
		$data['minYear']          = intval( $this->min_year );
		$data['allowPastDate']    = (bool) $this->allow_past_date;
		$data['twelveHourFormat'] = (bool) $this->twelve_hour_format;
		$data['includeTime']      = (bool) $this->include_time;

		return $data;
	}