This is the UNLOCK KEY for 'Leave Calendar' application, and removes the ads from the application.
You must have the Leave Calendar free installed for the key to work (to get it, look for "Leave Calendar" app in "More from developer" section on this page).
IMPORTANT! THE UNLOCK KEY DOES NOT HAVE A HOME SCREEN ICON AND CAN NOT BE "STARTED" - IT ONLY NEEDS TO BE INSTALLED!
The key will be automatically installed by Google Play. When the installation completes it should be listed as "Leave Calendar Key" in "Manage Applications" list of the device "Settings".
Everytime Leave Calendar app starts, it checks if the key is installed and removes the ads if the key is found. Please don't remove the key once installed, as it is needed everytime you run the Leave Calendar app.