Topic: General Data Protection Regulation (European Union)
The EU's General Data Protection Regulation, aka "GDPR", which was adopted April 2016, will be enforced as of 25 May 2018. The regulation contains provisions and requirements pertaining to the processing of personally identifiable information.
the calendar does not use so-called tracking cookies,
the calendar is only collecting the calendar ID (e.g. 'mycal') and numbers (i.e. User ID, and the current page, category, group, language) which are meaningless to other parties; so no sensitive data is stored in the cookies,
the data stored in cookies is serialized and as such not understandable by the human eye.
If you prefer, you could of course add a notice on your calendar web page saying that the calendar is using cookies and is compliant with the EU's GDPR.