Google Calendar is a time management and scheduling service developed by Google. Allows users to create and edit events, with options available for type and time. Available to anyone that has a Gmail account on both mobile and web versions.

Caldav is a protocol that allows different clients/servers to access scheduling information on remote servers as well as schedule meetings with other users on the same server or other servers. It extends WebDAV specification and uses iCalendar format for the data.

Apple calendar runs both the macOS and iOS mobile operating systems. Offering online cloud backup of calendars using Apple’s iCloud service, it can sync with Google Calendar and Microsoft Exchange Server. Users can schedule events in their day that include time, location, duration, and extra notes.