What's the best way to synchronize Calendar/iCloud with Outlook 2015

I've recently switched from using the native Mac Mail app to using Outlook 2015 for emails. It seems that Outlook automatically gives me access to my Mac address book. What's the best way to synchronise the Outlook calendar with the calendars in the native Mac Calendar app?

All the calendars I access using the Calendar app are actually stored on cloud services: some are on Google Calendar, others are on iCloud. Perhaps the easiest thing would be to access these cloud services directly from Outlook?