Computerized systems for synchronizing multiple calendars are provided. User activity is monitored via sensors and user devices associated with the user. Monitoring user activity includes detecting calendar activity associated with a set of calendars that includes a first calendar. A first calendar event associated with the first calendar is detected. A second calendar included in the set of calendars and associated with the first event is determined. The second calendar is determined based on the user activity, the first calendar, or the first event. The second calendar may be determined based on a synchronization profile associated with the first calendar. The second calendar is updated to include at least a portion of the first event. The first event is synchronized and/or shared with the second calendar. Only selective portions of the event data of the first event may be provided to the second calendar.