There are many great features in Google's Android 4.2 Jelly Bean OS, such as the beautiful-style world clock app and swipe control. If you have got an OTA update to 4.2 and installed that on your phone or tablet like nexus 7, it will have the ability to add different time zones within multiple cities you want at the single lock screen.
How to enable a world clock with current time of many places on your Android 4.2 lock screen
* From home screen, open the default Clock app.
* There is a small symbol in the bottom center of the screen. It is the location setting. Just touch on the icon, select on whatever cities you want included (e.g. Sydney, New York) and tap on Back button.
* Now go to the main lock screen panel, you should see the new world clock app. To reveal the full list of your cities, hold on the clock and swipe your finger downward. If you want to add its widget to a new panel, swipe to the right, tap a gray plus sign and then "Digital Clock" option.