old_contents: """
  Support for showing the time in a different time zone.
  
  For more details about this platform, please refer to the documentation at
  https://home-assistant.io/components/sensor.worldclock/
  """
  import logging
  
  import voluptuous as vol
  
  from homeassistant.components.sensor import PLATFORM_SCHEMA
  from homeassistant.const import (CONF_NAME, CONF_TIME_ZONE)
  import homeassistant.util.dt as dt_util
  from homeassistant.helpers.entity import Entity
  import homeassistant.helpers.config_validation as cv
  
  _LOGGER = logging.getLogger(__name__)
  
  DEFAULT_NAME = 'Worldclock Sensor'
  
  ICON = 'mdi:clock'
  
  TIME_STR_FORMAT = '%H:%M'
  
  PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
      vol.Required(CONF_TIME_ZONE): cv.time_zone,
      vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
  })
  
  
  def setup_platform(hass, config, add_devices, discovery_info=None):
      """Setup the World clock sensor."""
      name = config.get(CONF_NAME)
      time_zone = dt_util.get_time_zone(config.get(CONF_TIME_ZONE))
  
      add_devices([WorldClockSensor(time_zone, name)])
  
  
  class WorldClockSensor(Entity):
      """Representation of a World clock sensor."""
  
      def __init__(self, time_zone, name):
          """Initialize the sensor."""
          self._name = name
          self._time_zone = time_zone
          self._state = None
          self.update()
  
      @property
      def name(self):
          """Return the name of the device."""
          return self._name
  
      @property
      def state(self):
          """Return the state of the device."""
          return self._state
  
      @property
      def icon(self):
          """Icon to use in the frontend, if any."""
          return ICON
  
      def update(self):
          """Get the time and updates the states."""
          self._state = dt_util.now(time_zone=self._time_zone).strftime(
              TIME_STR_FORMAT)
  
new_contents: """
  Support for showing the time in a different time zone.
  
  For more details about this platform, please refer to the documentation at
  https://home-assistant.io/components/sensor.worldclock/
  """
  import asyncio
  import logging
  
  import voluptuous as vol
  
  from homeassistant.components.sensor import PLATFORM_SCHEMA
  from homeassistant.const import (CONF_NAME, CONF_TIME_ZONE)
  import homeassistant.util.dt as dt_util
  from homeassistant.helpers.entity import Entity
  import homeassistant.helpers.config_validation as cv
  
  _LOGGER = logging.getLogger(__name__)
  
  DEFAULT_NAME = 'Worldclock Sensor'
  
  ICON = 'mdi:clock'
  
  TIME_STR_FORMAT = '%H:%M'
  
  PLATFORM_SCHEMA = PLATFORM_SCHEMA.extend({
      vol.Required(CONF_TIME_ZONE): cv.time_zone,
      vol.Optional(CONF_NAME, default=DEFAULT_NAME): cv.string,
  })
  
  
  @asyncio.coroutine
  def async_setup_platform(hass, config, async_add_devices, discovery_info=None):
      """Set up the World clock sensor."""
      name = config.get(CONF_NAME)
      time_zone = dt_util.get_time_zone(config.get(CONF_TIME_ZONE))
  
      hass.loop.create_task(async_add_devices(
          [WorldClockSensor(time_zone, name)], True))
      return True
  
  
  class WorldClockSensor(Entity):
      """Representation of a World clock sensor."""
  
      def __init__(self, time_zone, name):
          """Initialize the sensor."""
          self._name = name
          self._time_zone = time_zone
          self._state = None
  
      @property
      def name(self):
          """Return the name of the device."""
          return self._name
  
      @property
      def state(self):
          """Return the state of the device."""
          return self._state
  
      @property
      def icon(self):
          """Icon to use in the frontend, if any."""
          return ICON
  
      @asyncio.coroutine
      def async_update(self):
          """Get the time and updates the states."""
          self._state = dt_util.now(time_zone=self._time_zone).strftime(
              TIME_STR_FORMAT)
  
subject: Migrate to async (#4135)