Calendar subscriptions have existed for a while, but are just recently starting to catch on. The idea first gained traction in 2009 through the introduction of the iCalendar protocol (RFC 5545)
, which greatly simplified broadcasting operations for large organizations. Google Calendar actually has built-in streaming features and is fully compatible with Outlook and Apple Calendar, but for some reason this appears underutilized in practice. However, calendar subscriptions appear to be gaining in popularity, especially at MIT.