What are some alternatives?
When comparing ApPHP Calendar and VCalendar, you can also consider the following products
Google Calendar - Spend less time managing your day & more time enjoying it
Teamup Calendar - Cloud-based calendaring using capability URL, application developed in Zurich, Switzerland.
Teamweek - A project management software to help you get the best overview. Plan fast, change plans faster!
Campaign Calendar - Campaign Calendar by Bracket Labs builds a marketing calendar from your Salesforce Campaigns.
Apple Calendar - Calendar is a personal calendar app made by Apple Inc. that runs on both the macOS desktop operating system and the iOS mobile operating system.
Cronofy - Unified Calendar API for developers