Companion

Custom sync column to store the last known ETag of an event.

Custom sync column to store sync flags of an event.

Custom sync column to store the Schedule-Tag of an event.

Custom sync column to store the SEQUENCE of an event.

VEVENT CATEGORIES are stored as an extended property with this ExtendedProperties.NAME.

Google Calendar uses an extended property called iCalUid for storing the event's UID, instead of the standard Events.UID_2445.

VEVENT URL is stored as an extended property with this ExtendedProperties.NAME. The URL is directly put into ExtendedProperties.VALUE.