Internet Calendars are calendars that are shared through the Internet. These calendars are based upon a global Internet standard that allows calendar information to be exchanged between people regardless of the application that is used to create or view the information. Internet Calendars use the iCalendar format (not to be confused with Apple’s iCal) and the .ics file name extension.

An Internet Calendar Subscription is a calendar that you open and view, for example, either as a webpage or directly in calendar apps such as Outlook, iOS, MAC, Microsoft 365, Outlook.com, or Google Calendar. Internet Calendar Subscriptions are updated automatically and thus dynamic. Subscribing to a calendar may be as easy as a click on a link to download the calendar, or someone can send you a link to the Internet Calendar Subscription in an email message. This link is an Internet web address that begins with webcal:// and ends with a file name that has the .ics file extension.