Why do we need a vCalendar file generator? The output of your app is a vCalendar file which is then imported into a Calendar app either manually or through the integration of email and calendar services. So in the end, people still have to use a calendar app. It is much easier to create an event on a calendar app and send the invitation which is actually sending emails with a vCalendar file as an attachment. Besides that, most calendar apps allow exporting the event as a vCalendar file also.