An electronic world clock device indicates a time in connection with a designated region based on a time difference in a reference region to be stored, and comprises clock means for counting a present time in a specified home region and memory means for storing various regions and names of the countries...http://www.google.com.hk/patents/US5448532?utm_source=gb-gplus-share專利 US5448532 - Electronic world clock device for indicating times for various spots in the world
