Fix and improve monthly sync information

contributing/index.md

@@ -13,7 +13,9 @@ If you have any questions, don't hesitate to ask. We are happy to help you.
 
 ## Monthly sync
 
-We have a monthly sync meeting where we discuss the state of the project and what we want to do in the future. You can find the [meeting board](https://github.com/orgs/voxpupuli/projects/10/) here. The [zoom link](https://perforce.zoom.us/j/91219793310?pwd=M0pPRklhd0lhL2V6ZldQd1BZRCsvQT09) is always the same, so you can join us every month. We meet every second tuesday of the month at 15:30 UTC.
+We have a monthly sync meeting where we discuss the state of the project and what we want to do in the future. You can find the [meeting board](https://github.com/orgs/voxpupuli/projects/10/) here. The [zoom link](https://perforce.zoom.us/j/91219793310?pwd=M0pPRklhd0lhL2V6ZldQd1BZRCsvQT09) is always the same, so you can join us every month. We meet every second tuesday of the month at 16:30 [CET](https://www.timeanddate.com/time/zones/cet)/[CEST](https://www.timeanddate.com/time/zones/cest). You can [import this event in your calendar](voxpupuli-monthly-sync.ics).
+
+<p id="nextmeeting"></p>
 
 ## Guidelines
 
@@ -22,3 +24,25 @@ We have a monthly sync meeting where we discuss the state of the project and wha
 - If you have question about security, please follow our [security policy](https://voxpupuli.org/security/).
 - General and more specific documentation can be found on our [docs](https://voxpupuli.org/docs/).
 - In the project you want to work on, check their own contribution guidelines most often found in the README.md or CONTRIBUTING.md file.
+
+<script src="https://momentjs.com/downloads/moment.min.js"></script>
+<script src="https://momentjs.com/downloads/moment-timezone-with-data-10-year-range.js"></script>
+<script type="application/javascript">
+const myTimeZone = moment.tz.guess();
+const eventTimeZone = "Europe/Berlin";
+
+let nextMeeting = moment.tz(eventTimeZone).startOf('month').add(1, 'week').hours(16).minutes(30);
+dayOffset = 2 - nextMeeting.day();
+if (dayOffset < 0) dayOffset += 7;
+nextMeeting.add(dayOffset, 'days');
+
+if (nextMeeting.isBefore(moment.tz(eventTimeZone).add(1, 'hour'))) {
+  nextMeeting = moment.tz(eventTimeZone).startOf('month').add(1, 'month').add(1, 'week').hours(16).minutes(30);
+  dayOffset = 2 - nextMeeting.day();
+  if (dayOffset < 0) dayOffset += 7;
+  nextMeeting.add(dayOffset, 'days');
+}
+
+document.getElementById('nextmeeting').innerHTML += "Next monthly sync: " + nextMeeting.tz(myTimeZone).calendar() + " (" +
+ nextMeeting.tz(myTimeZone).format() + ")";
+</script>

contributing/voxpupuli-monthly-sync.ics

@@ -0,0 +1,68 @@
+BEGIN:VCALENDAR
+PRODID:-//K Desktop Environment//NONSGML libkcal 4.3//EN
+VERSION:2.0
+BEGIN:VTIMEZONE
+TZID:Europe/Berlin
+BEGIN:STANDARD
+TZNAME:CET
+TZOFFSETFROM:+0000
+TZOFFSETTO:+0100
+DTSTART:19791231T230000
+RDATE:19791231T230000
+END:STANDARD
+BEGIN:DAYLIGHT
+TZNAME:CEST
+TZOFFSETFROM:+0100
+TZOFFSETTO:+0200
+DTSTART:19810329T020000
+RRULE:FREQ=YEARLY;BYMONTH=3;BYDAY=-1SU
+END:DAYLIGHT
+BEGIN:DAYLIGHT
+TZNAME:CEST
+TZOFFSETFROM:+0100
+TZOFFSETTO:+0200
+DTSTART:19800406T020000
+RDATE:19800406T020000
+END:DAYLIGHT
+BEGIN:STANDARD
+TZNAME:CET
+TZOFFSETFROM:+0200
+TZOFFSETTO:+0100
+DTSTART:19971026T030000
+RRULE:FREQ=YEARLY;BYMONTH=10;BYDAY=-1SU
+END:STANDARD
+BEGIN:STANDARD
+TZNAME:CET
+TZOFFSETFROM:+0200
+TZOFFSETTO:+0100
+DTSTART:19800928T030000
+RRULE:FREQ=YEARLY;UNTIL=19961027T030000;BYMONTH=9;BYDAY=-1SU
+RDATE:19950924T030000
+END:STANDARD
+END:VTIMEZONE
+BEGIN:VEVENT
+DTSTAMP:20241227T225300Z
+CREATED:20241227T225300Z
+UID:6A104D48-6E0B-455A-8287-A15FB58FD654
+LAST-MODIFIED:20241227T225910Z
+DESCRIPTION:Meeting Board:\nhttps://github.com/orgs/voxpupuli/projects/10/\
+ n\nZoom:\nhttps://perforce.zoom.us/j/91219793310?pwd=M0pPRklhd0lhL2V6ZldQd
+ 1BZRCsvQT09
+SUMMARY:Vox Pupuli Monthly Sync
+LOCATION:Online
+DTSTART;TZID=Europe/Berlin:20241210T163000
+DTEND;TZID=Europe/Berlin:20241210T173000
+TRANSP:OPAQUE
+CLASS:PUBLIC
+BEGIN:VALARM
+TRIGGER;RELATED=START;VALUE=DURATION:-PT1H
+ACTION:DISPLAY
+SUMMARY:Vox Pupuli Monthly Sync
+DESCRIPTION:Meeting Board:\nhttps://github.com/orgs/voxpupuli/projects/10/\
+ n\nZoom:\nhttps://perforce.zoom.us/j/91219793310?pwd=M0pPRklhd0lhL2V6ZldQd
+ 1BZRCsvQT09
+END:VALARM
+RRULE:FREQ=MONTHLY;BYDAY=2TU
+END:VEVENT
+X-KDE-ICAL-IMPLEMENTATION-VERSION:1.0
+END:VCALENDAR