diff --git a/.gitignore b/.gitignore
index 008e122..03d9a0a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -202,3 +202,8 @@ $RECYCLE.BIN/
 *.lnk
 
 # End of https://www.toptal.com/developers/gitignore/api/windows,linux,macos,hugo,pycharm+all,vim,direnv
+
+### CCCB ###
+# The calendar the site reads its events from is published next to the site and
+# only downloaded here to look at the site locally, see the README.
+/static/calendars/
diff --git a/README.md b/README.md
index 5f72bd0..c14ea17 100644
--- a/README.md
+++ b/README.md
@@ -29,20 +29,31 @@ This is the website of the CCCB.
 
 Every change you make on the project will be reflected in your browser as long as `hugo serve` is running.
 
-The *"Nächste Veranstaltungen"* table on the home page is generated by post-processing in `./build.sh`, not by Hugo, so
-it is **not** visible under `hugo serve`. To preview the fully built site (including the home-page calendar), or to
-ready the site for upload, run:
+The *"Nächste Veranstaltungen"* table on the home page and the calendar under `/verein/calendar/` are rendered in the
+browser by `static/js/upcoming.js` and `assets/js/calendar.js`. Both fetch `/calendars/all.ics`, which is **not**
+generated by Hugo and is not part of this repo — it is published separately on the web server. Without it both tables
+stay empty. Download the published calendar into `static/`, which Hugo serves under the same path, and they work
+locally, under `hugo serve` as well as in a built site:
+
+```shell
+mkdir -p static/calendars
+curl -o static/calendars/all.ics https://berlin.ccc.de/calendars/all.ics
+```
+
+The file is only there to look at the site, it is not checked in. Download it again whenever you want the events that
+are currently published.
+
+Hugo does generate an `.ics` feed per section (for example `/veranstaltungen/index.ics`) from the `dtstart`, `dtend`
+and `rrule` front matter of the pages in `content/veranstaltungen/`, using the `.ics` templates under `layouts/`.
+
+To build the site for upload, run:
 
 ```shell
 ./build.sh
-python3 -m http.server -d public 1313
 ```
 
-`build.sh` replaces the `CALENDAR` placeholder in `index.html` with the upcoming-events table. It depends on Python
-with the `icalendar`, `python-dateutil`, and `pytz` packages, plus a `de_DE.UTF-8` locale (used to format weekday
-names). Inside `nix develop` these are provided automatically.
-
-To build with *nix*: `nix build '.?submodules=1#production-content'`
+This deletes `public/` and runs `hugo` with the parameters from `.hugo-params`. To build with *nix* instead:
+`nix build '.?submodules=1#production-content'`
 
 ## Making a change
 
@@ -59,8 +70,7 @@ To build with *nix*: `nix build '.?submodules=1#production-content'`
 
 ## Nix stuff
 
-- After entering the shell with `nix develop`, hugo is available and `hugo serve` should work
-- Python including required packages will be available, so the `build.sh` should work without a venv
+- After entering the shell with `nix develop`, hugo is available and `hugo serve` and `./build.sh` should work
 - You can build the staging and production builds with `nix build .#staging-content` and
   `nix build .#production-content`
 - Do not update the nixpkgs branch - 25.05 contains a newer hugo version that is incompatible with the theme (last