CI: Set timezone to Europe/Berlin

Evaluation of the ical data uses the local time when formating the output string as the input data uses UTC.

.gitlab-ci.yml

@@ -1,3 +1,6 @@
+variables:
+  TZ: Europe/Berlin
+
 stages:
   - build
   - deploy

themes/ccchh/layouts/shortcodes/calendar-table.html

@@ -12,7 +12,7 @@
     {{- if eq ._type "vevent"}}
     <tr>
       {{- $start := time .dtstart }}
-      <td style="font-variant-numeric: tabular-nums;">{{ $start.Local | time.Format "Mon, 2006-01-02 15:04" }}</td>
+      <td style="font-variant-numeric: tabular-nums;">{{ $start.Local.Format "Mon, 2006-01-02 15:04" }}</td>
       <td>{{ .summary }}</td>
       <td>{{ .location }}</td>
     </tr>