A human editable (.txt) and machine readable (.ics) calendar-list.
You can create a text with dates:
21.3.2016, 10–11, Meeting
22.3.2016, Birthday
This will result in two calendar entries. The first is titled "Meeting" and has a time-range, the second is a whole day event with a title of "Birthday".
If you have many repeating events you can also have a template-like header:
---
title:
prefix: "Meetup"
join: " – "
date: 18:00–22:00
notes: bring beer.
---
22.2.2016, HTML
29.2.2016, JS
This will produce two events, one with the Title Meetup – HTML and one with Meetup – JS. Both have a note and a time-range.