Privacy Policy

App: Monthly Door Calendar (German: „Monatskalender mit Türchen“)
Developer and controller: Günter Struck, Lönsberg 6, 45136 Essen, Germany
Contact: caresms@online.de
Last updated: October 2026

This English version is provided for convenience. In case of doubt, the German version is authoritative.

Summary: The Monthly Door Calendar app requires no account and uses no cookies and no personal tracking. Your settings and progress stay on your device only. When the app is loaded over the internet, the hosting provider (Vercel) technically processes your IP address; in addition, the app anonymously counts how often it is opened at kalender356.vercel.app (see section 9a).

1. Controller

The controller within the meaning of the GDPR is the developer of the app:
Günter Struck, Lönsberg 6, 45136 Essen, Germany
Email: caresms@online.de

2. What data does the app process?

The app requires neither an account nor registration. It does not request permissions such as location, camera, microphone or contacts. Permission for notifications is only requested if you turn on the app reminder yourself (section 5). Only the following information is stored on your device (local storage “Local Storage” or “IndexedDB”):

which calendar doors you have opened,
the selected month and year,
your color scheme setting (light/dark),
the assignment of quotes and door positions in the calendar,
a flag indicating whether the app was installed,
if you use the reminder: the chosen time, whether the app notification is on, the language of the notification, and the date on which you last opened today’s door or were last reminded.

This information is not linked to your person and is not transmitted to the developer. The developer has no access to it.

The app’s language (German or English) is derived from your browser or device language setting each time the app starts.

Legal basis: Storing these settings is technically necessary to provide the service you requested (Section 25 (2) no. 2 TDDDG, German Telecommunications Digital Services Data Protection Act). Where personal data is processed, the legal basis is Art. 6 (1) (f) GDPR (legitimate interest in a functioning, usable calendar). A consent request is therefore not required.

3. No disclosure to third parties, no advertising

The app does not send any content or settings to the developer or to third parties. The only exception is the anonymous page-view count (section 9a). It contains no advertising or personal tracking services, no cookies, no embedded third-party fonts, scripts or content and no social media plugins. No data is sold or used for advertising.

4. Offline function (service worker)

The app registers a service worker and stores its own files (HTML, CSS, JavaScript, quotes, images) in your device’s cache so that it also works without an internet connection. No personal data is stored in the process. The cache is renewed automatically with app updates.

5. Daily reminder (optional)

The reminder is off until you set it up yourself via “Reminder”. There are two ways, neither uses a server of the developer:

Calendar event: The app creates a calendar file (.ics) on your device with a daily event at the chosen time and a link to the app. What happens to the event afterwards (e.g. syncing via Google, Apple or Microsoft) is determined by your calendar app or its provider under their privacy terms.
App notification: In the installed app (Chrome/Edge) the browser may occasionally wake the app in the background (“Periodic Background Sync”). The app then checks locally whether the chosen time has been reached and today’s door is still closed, and shows at most one notification per day. No push service is used; no data is transmitted.

The legal basis is your explicit request (Section 25 (2) no. 2 TDDDG) or your consent by turning the feature on (Art. 6 (1) (a) GDPR). You can turn the notification off at any time in the “Reminder” dialog or revoke the permission in your device or browser settings. You delete a calendar event in your calendar app.

6. Sharing a quote

Only when you tap “Share” in the quote window does the app pass the quote text, the author and a link to the app to your device’s share menu or copy them to the clipboard. You decide which app receives the data; its terms apply to any further processing. The developer receives nothing.

7. Live demo

The live demo and the mini demos present the app with sample states. They store nothing and do not change your calendar progress. The background music is only loaded when a demo starts, from the same server as the app (Vercel); no connection to the music provider is made.

8. External links

The quotes link to Wikipedia (de.wikipedia.org or en.wikipedia.org depending on the language). These links only open in a new tab or browser when you tap them yourself. Only then is data (e.g. your IP address) transmitted to the Wikimedia Foundation; its privacy policy applies. The developer has no influence on its data processing.

9. Hosting

The app files are provided via the Vercel platform (Vercel Inc., 440 N Barranca Avenue #4133, Covina, CA 91723, USA). When the app is loaded or updated, Vercel technically processes connection data (e.g. IP address, time, requested file, browser/device information) in server log files; delivery may take place via servers in different regions. This is based on Art. 6 (1) (f) GDPR (secure, fast and efficient provision of the app). A transfer to the USA is possible; according to Vercel, it relies on the EU-US Data Privacy Framework or standard contractual clauses. Vercel acts as a processor under a data processing agreement (Art. 28 GDPR). Log data is only stored for a short time; the developer does not analyse it and uses it at most to troubleshoot technical problems. Once loaded, the app also works offline. More information: Vercel Privacy Policy.

The app’s source code is publicly available on GitHub. Using the app does not create any connection to GitHub.

9a. Anonymous usage count

To see whether the app is used at all, it counts page views at kalender356.vercel.app with Vercel “Web Analytics”. In detail:

No cookies and no other identifier stored on or read from your device.
Only the requested address without query string and fragment, the referring page and coarse technical information such as browser, operating system, device type and country are transmitted. According to Vercel, the IP address is not stored; visitors are only grouped within a single day using a non-reversible hash.
No content and no usage details: nothing is sent about which doors you open, which quotes you read or share, or which settings you choose – only that the app was opened.
If “Do Not Track” or Global Privacy Control is enabled in your browser, nothing is counted. Nothing is counted while offline either.

The legal basis is our legitimate interest (Art. 6 (1) (f) GDPR) in finding out, with as little data as possible, whether the app is used. Nothing is stored on or read from your device for this purpose (Section 25 TDDDG therefore does not apply). Vercel acts as a processor here as well.

10. Storage period and deletion

Locally stored data remains until you delete it. You can remove it at any time by clearing the app data or app storage in your device or browser settings, or by uninstalling the app. Your browser’s “clear site data” function also removes the offline cache and the reminder data.

11. Your rights

The developer does not store any personal data about you himself; the short-lived server log files of the hosting provider (section 9) cannot be attributed to a person. He can therefore generally not attribute or disclose any data to you. Regardless of this, under the GDPR you have the right of access, rectification, erasure, restriction of processing, data portability, objection and withdrawal of consent. You also have the right to lodge a complaint with a data protection supervisory authority; in North Rhine-Westphalia this is the LDI NRW.

12. Children

The app is aimed at a general audience and does not collect personal data from anyone, including children.

13. Changes

This policy may be updated, for example when new app features are added. The current version is always available at this address.

14. Contact

Please send privacy questions to: Günter Struck, caresms@online.de

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