Tribe - default start/end time helper

/**
 * Helps to change the default start/end times for new event.
 */
class Change_Tribe_Default_Event_Times
{
    const TWELVEHOUR = 12;
    const TWENTYFOURHOUR = 24;

    protected $start = 9;
    protected $end = 11;
    protected $mode = self::TWELVEHOUR;


    /**
     * Provide the desired default start and end hours in 24hr format (ie 15 = 3pm).
     *
     * @param $start_hour
     * @param $end_hour
     */
    public function __construct($start_hour, $end_hour) {
        $this->settings($start_hour, $end_hour);
        $this->add_filters();
    }


    protected function settings($start_hour, $end_hour) {
        $this->set_mode();
        $this->start = $this->safe_hour($start_hour);
        $this->end = $this->safe_hour($end_hour);
    }


    protected function add_filters() {
        add_filter('tribe_get_hour_options', array($this, 'change_default_time'), 10, 3);
        add_filter('tribe_get_meridian_options', array($this, 'change_default_meridian'), 10, 3);
    }


    protected function set_mode() {
        if (strstr(get_option('time_format', TribeDateUtils::TIMEFORMAT), 'H'))
            $this->mode = self::TWENTYFOURHOUR;
    }


    protected function safe_hour($hour) {
        $hour = absint($hour);
        if ($hour < 0) $hour = 0;
        if ($hour > 23) $hour = 23;
        return $hour;
    }


    public function change_default_time($hour, $date, $isStart) {
        if ('post-new.php' !== $GLOBALS['pagenow']) return $hour; // Only intervene if it's a new event

        if ($isStart) return $this->corrected_time($this->start);
        else return $this->corrected_time($this->end);
    }


    /**
     * If working in the 12hr clock, converts the hour appropriately.
     *
     * @param $hour
     * @return int
     */
    protected function corrected_time($hour) {
        if (self::TWENTYFOURHOUR === $this->mode) return $hour;
        if ($hour > 12) return $hour - 12;
        return $hour;
    }


    public function change_default_meridian($meridian, $date, $isStart) {
        if ('post-new.php' !== $GLOBALS['pagenow']) return $meridian; // Only intervene if it's a new event

        $meridian = 'am';
        if ($isStart && 12 <= $this->start) $meridian = 'pm';
        if (! $isStart && 12 <= $this->end) $meridian = 'pm';

        if (strstr(get_option('time_format', TribeDateUtils::TIMEFORMAT), 'A'))
            $meridian = strtoupper($meridian);

        return $meridian;
    }
}

// If you mostly deal with night time soirees you could set the default start time
// to 7pm and end time to 11pm - but remember to do so with the 24hr clock
new Change_Tribe_Default_Event_Times(19, 23);

// If you run early morning workouts you might set the default start time to
// 5am and end time to 6am
new Change_Tribe_Default_Event_Times(5, 6);