To set up calendar synchronization in EmClient follow these steps:
Create a connection to access the calendar in WebMail.
Go to "
Menu → Tools → Accounts»:

Click the add a new account button:

Select "
Thecalendar → CalDAV" and press "
Further»:

Fill in the fields and click "
Further»:

Specify an arbitrary account name that will be used to define the calendar, and click "
Further»:

Finish creating a new account and check the calendar sync.