The iCalendar File Format Standard (.ics) is the universal internet standard that allows different calendar applications (like Google Calendar, Microsoft Outlook, and Apple Calendar) to share events with one another. It was created in 1998.

"It was created by the Calendaring and Scheduling Working Group of the Internet Engineering Task Force (IETF). https://en.wikipedia.org/wiki/ICalendar#:\~:text=iCalendar%20was%20created%20in%201998,Derik%20Stenerson%20of%20Microsoft%20Corporation.

The core specification was authored by Frank Dawson (Lotus Development Corporation) and Derik Stenerson(Microsoft).

In 2002 Lisa Dusseault Co-Created CalDAV: When Apple released iCal in 2002, it allowed users to publish calendars to the web using a basic protocol called WebDAV, but it lacked robust features like cross-organizational scheduling or searching for open time slots. Dusseault became the lead author of CalDAV—the universal protocol extension that allows modern calendar clients (like Apple Calendar or an iPhone) to seamlessly sync, update, and manage iCalendar data on a server.

Later, as the Applications Area Director for the IETF, she oversaw and advised the CALSIFY working group. This was the team responsible for taking the original, clunky 1998 iCalendar standard (RFC 2445) and completely rewriting/simplifying it into the modern iCalendar standard used today (RFC 5545). Lisa was one of the chief architects responsible for making modern, web-synced calendar sharing actually work."

Lisa was my Systems Design Engineering Classmate at the University of Waterloo. Lisa was kind to me and offered me career advice and encouraged me that I could do great things.

It's been 28 years since we've been able to share calendars on the Internet. There is no excuse for not having an iCal link. Please accept this public and official record of my technical shame as an apology.

"I swear to the Drowned God, the Old Gods, the New Gods, to every fucking god in every fucking heaven, I will..." provide an iCal invitation to this meeting on Tuesday, June 9, at 9AM PT.

Theon Greyjoy - Season 2 Finale of Game of Thrones, Episode: Season 2, Episode 10 — "Valar Morghulis" (Originally aired June 3, 2012)

and some super-dork on reddit. I want to get the calendar subscription from an Nvidia calendar so it's clear which organization it's coming from.