ICS/iCal files are plain text files that include calendar event details about an event, such as a description, time or location. The ICS format is used for sending people meeting requests but also a popular means for subscribing to holiday or birthday calendars.
Adding an ICS file to Taxi:
It is possible to add in an ICS file to an email you're building in Taxi. You'd need to host the file yourself. Once you've done this, you can then then insert a link to the file behind either a normal link, or a button or image.
Using the above tool you can put all your event info in, generate and it gives you a file which you then host (where you host your images) then upload that file path link to the button.