To sync Charms calendar with Apple iOS devices:
Go to Settings:
Tap Mail > Contacts > Calendars.
From Accounts, tap Add Account.
At the Add Account screen, tap Other.
From Calendars, tap Add Subscribed Calendar.
For the Server value, enter the URL of the public calendar:
Tap Next in the upper right corner.
It will verify the server and then show a subscription page. Change the description if you like.
Tap Save to save the subscription.
To sync Charms calendar with Android devices:
(you must use your Google account and have a Google calendar created)