Google Calendar Sync
Thanks to the integration with Google Calendar, the admin can view bookings on his/her own Google Calendar. The booking synchronization is a one-way sync (from your site to Google Calendar).
The Google Calendar sync is available only for the admin: you can set a unique Google Calendar account to synchronize all bookings with your Google Calendar (in YITH > Booking > Google Calendar)
This feature is useful to see all bookings in a Google Calendar, but it’s not useful to prevent overbooking.
iCal Booking Sync
On the other hand, with regards to “Booking synchronization with external services” (such as Airbnb and Booking.com), you can add youe own ICS files (iCal) to synchronize a specific product with external services in “Edit product” page > Booking Sync tab.
- you can set the external calendars
- you can use this URL to add it to your external services
However, you cannot use the iCal Booking Sync to manage bookings through Google Calendar; or better, you can create 2 calendars (One and Two) on Google Calendar
- add the Booking iCal URL to your Google Calendar One
- add the iCal url of your Google Calendar Two in the external calendars table (in Booking Sync tab)
This to prevent double sync issues.
However, on the other hand, about iCal, Google Calendar synchronizes external calendars each XX hours, so if you create a booking in your site it’ll be not synchronized instantaneously by Google Calendar, but it’ll be synchronized after some hours.
Google specifies it could take up to 12 hours to be synchronized (you can read it here: https://support.google.com/calendar/answer/37100?hl=en&ref_topic=1672445)