I found the solution. The docker container was not aware of the correct timezone. I found this https://github.com/bastilimbach/docker-MagicMirror/issues/15 and added this to my docker-compose.yml

    environment:
      - TZ=Europe/Berlin
      - SET_CONTAINER_TIMEZONE=true
      - CONTAINER_TIMEZONE=Europe/Berlin

My calendars are created in Google Calendar.

Here is one of my “offending” calendar entries. It gets rendered on every second tuesday (as expected), but also on the following wednesday, which is wrong.

BEGIN:VEVENT
DTSTART;VALUE=DATE:20200602
DTEND;VALUE=DATE:20200603
RRULE:FREQ=WEEKLY;WKST=MO;INTERVAL=2;BYDAY=TU
DTSTAMP:20200603T175106Z
UID:secret@google.com
CREATED:20200603T174826Z
DESCRIPTION:Städning
LAST-MODIFIED:20200603T174826Z
LOCATION:
SEQUENCE:0
STATUS:CONFIRMED
SUMMARY:Städning
TRANSP:TRANSPARENT
BEGIN:VALARM
ACTION:DISPLAY
DESCRIPTION:This is an event reminder
TRIGGER:-P0DT0H30M0S
END:VALARM
END:VEVENT

@Sean I tried this first, then I tried forceLocalTZ: false, that is why it’s still there. Neither works.

I have the same problem with full day events spanning 2 days. I don’t have any third party calendars, just my own. Five in total, all from Google. All have similar config, just URL and icon that differs.

{
      module: "MMM-CalendarExt2",
      config: {
        calendars: [
          {
            forceLocalTZ: false,
            beforeDays: 0,
            afterDays: 60,
            icon: "mdi-castle",
            url: "<removed>"
          },
        ],
        views: [
          {
            mode: "week", 
            slotCount: 3,
            locale: "sv-SE",
            position: "middle_center",
          },
        ],
        scenes: [
          {
            name: "DEFAULT",
          },
        ],  
      }
    },

I use docker to host MagicMirror.

This is my package-lock.json

{
  "name": "MMM-CalendarExt2",
  "version": "1.0.9",
  "lockfileVersion": 1,
  "requires": true,
  "dependencies": {
    "ical-expander": {
      "version": "2.1.0",
      "resolved": "https://registry.npmjs.org/ical-expander/-/ical-expander-2.1.0.tgz",
      "integrity": "sha512-G2J1HIFbL3CPr7tz7U4UYmB8l3Iu16ib3ddzbveCJyvmvjo3MqAye+Izts2H/dOJuSMxYx1DolcEN5TslcNHlg==",
      "requires": {
        "ical.js": "1.2.2"
      }
    },
    "ical.js": {
      "version": "1.2.2",
      "resolved": "https://registry.npmjs.org/ical.js/-/ical.js-1.2.2.tgz",
      "integrity": "sha1-WbUXNiqPYdzgNC/mfet8IN0Rn24="
    },
    "moment": {
      "version": "2.26.0",
      "resolved": "https://registry.npmjs.org/moment/-/moment-2.26.0.tgz",
      "integrity": "sha512-oIixUO+OamkUkwjhAVE18rAMfRJNsNe/Stid/gwHSOfHrOtw9EhAY2AHvdKZ/k/MggcYELFCJz/Sn2pL8b8JMw=="
    },
    "moment-timezone": {
      "version": "0.5.31",
      "resolved": "https://registry.npmjs.org/moment-timezone/-/moment-timezone-0.5.31.tgz",
      "integrity": "sha512-+GgHNg8xRhMXfEbv81iDtrVeTcWt0kWmTEY1XQK14dICTXnWJnT0dxdlPspwqF3keKMVPXwayEsk1DI0AA/jdA==",
      "requires": {
        "moment": ">= 2.9.0"
      }
    }
  }
}