Now when you share event details of your Google Calendar with others, they can subscribe to receive email notifications when you make certain changes to new and existing events. To increase transparency, Google will also notify you when a person subscribes to receive your calendar updates.

Calendar users who have at least been granted “See event details” can choose to receive notifications when events are:

• Created.
• Changed.
• Canceled.
• RSVPed.
• Coming up.

They can also choose to receive a daily agenda for the calendar that they subscribe to.

To subscribe to calendar notifications:

• Open Google Calendar and locate the specific calendar under My calendars or Other calendars.
• Click on the Options menu.
• Choose Settings.
• Add:
  • Event notifications. 
  • All-day event notifications.
  • Other notifications.

For more information, see Be informed when someone subscribes to email notifications of your Calendar.