This Privacy Policy explains how we handle your data in the MyDaysX apps (the classic MyDaysX app and the new MyDaysX app, internal codename “MDX2”, which are being merged) and on the website blog.mydaysx.club.
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Christian Albert Mueller, Schwanseestr. 47, 81549 Munich, Germany · info@mydaysx.club · VAT ID: DE298983586.
We have appointed an external Data Protection Officer:
Heiko Jonny Maniero, DGD Deutsche Gesellschaft für Datenschutz · heiko.maniero@dg-datenschutz.de · Tel. +49 (0)800 62 64 376.
You have the right to lodge a complaint with a data protection supervisory authority. The authority competent for us is the Bavarian State Office for Data Protection Supervision (BayLDA), Promenade 18, 91522 Ansbach, Germany. You may also contact the authority in your country of residence.
Period days, fertility, ovulation, symptoms, intimate events, notes, basal temperature, weight and lab values you enter yourself (estradiol, FSH, LH, progesterone, total testosterone and TSH, together with the draw date, the unit, the cycle phase and an optional lab name and note) are health data (special category, Art. 9 GDPR). We process them only to provide the tracking and prediction features, on the basis of your explicit consent (Art. 9(2)(a) GDPR), given during onboarding and withdrawable at any time (turn the features off, erase your data, or delete the app). This data is stored on your device; the new app does not upload it to our servers.
Your birthdate, entered during onboarding, is stored on your device only — it is used for the 16+ age verification and optional fun features, and is never transmitted to our servers.
If you create a server backup (classic app) or restore an older backup during migration, the data is stored over an encrypted (HTTPS) connection on our server in the EU (Hetzner, Finland). Legal basis: your consent (Art. 6(1)(a), Art. 9(2)(a) GDPR). You may also create a local backup file, optionally encrypted with a passphrase.
If you enable health sync, the app reads/writes your menstrual flow and basal body temperature to Apple Health (iOS) or Health Connect (Android) on your device. This data is governed by Apple/Google, stays on your device, and is never transmitted to our servers or shared with advertising/analytics providers. You can disable sync and revoke access at any time.
We process your email only if you subscribe to our newsletter or set a recovery email, for those purposes only (Art. 6(1)(a)/(b) GDPR). The newsletter uses double opt-in (you confirm via a link) and can be unsubscribed at any time.
The classic MyDaysX app uses third-party analytics and diagnostics SDKs — Google Firebase Analytics, Google Crashlytics and GameAnalytics — and, for advertising, Google AdMob with ironSource/Unity LevelPlay mediation (incl. Unity Ads). These may process coarse device information and, where you granted the permission, approximate location. Your manually-entered cycle data is never shared with them.
The new MyDaysX app sends anonymous statistics to our own server in the EU (AWS, Frankfurt) — no advertising identifier, no precise location, never your name or notes, and no IP address is stored. (1) Anonymous product statistics are on by default (no consent prompt, because the data is anonymous); you can switch them off anytime in Settings → “Share anonymous stats.” A randomly generated identifier rotates daily and is never linked to you or your cycle/health data. They cover country region (from your device language, never your IP), app language, theme, app version, which features are used, and coarse activity bands (how many days you have been active, how long you have used the app). (2) Research & data products (separate, explicit consent) — additionally coarse, irreversibly anonymous ranges and counts: cycle- and period-length ranges, cycle regularity, age band, symptom and mood frequencies per cycle phase, intimacy frequency (a count, no details), pregnancy/ovulation-test outcome counts, pregnancy starts and contraception type. These are aggregated, protected with k-anonymity and noise, may be turned into synthetic datasets, and may be shared with researchers and research partners, but are never sold — they describe patterns, never a person, and can never be traced back to you. Withdrawing either consent stops future contributions immediately and deletes unsent data on the device; already-published anonymous aggregates contain nothing traceable to you. We record the consent version and date (Art. 7 GDPR). Legal basis: your consent (Art. 6(1)(a), Art. 9(2)(a) GDPR for the on-device derivation).
Anonymous crash/error events may be sent to our EU server (AWS, Frankfurt) to fix bugs; no cycle or health data is included. Legal basis: legitimate interest (Art. 6(1)(f) GDPR).
If you use Invite Friends, we process only an anonymous, resettable install identifier and your referral code to credit invitations. We do not access your contacts. Legal basis: Art. 6(1)(b)/(f) GDPR.
The free version shows ads via Google AdMob (and its mediation), which may use an advertising identifier as described in Google’s policies. Your cycle and health data are never shared with AdMob or any ad network. Where required, advertising is shown only after you have answered Google’s consent form (Google User Messaging Platform); on iOS, Apple’s tracking prompt (App Tracking Transparency) follows.
Optional “Pro” purchases are processed by Apple App Store or Google Play. They are the merchants of record and handle the payment and any statutory withdrawal; we never receive or store your payment-card details.
The app may ask for device permissions (e.g. notifications, photos for attaching a picture to an entry, health access). Permissions are optional and used only for the stated feature; you can manage them in your device settings.
Our website serves the static pages you are reading. This website sets no cookies and loads no analytics, advertising or social-media tools. On the contact page, a bot check (Cloudflare Turnstile, see section 4) loads only when you start using the form; it stores a small technical entry in your browser and protects the form against spam (Art. 6(1)(f) GDPR, and § 25(2) no. 2 TDDDG because it is needed for the form you asked to use). When you visit the website, our hosting provider (Namecheap, USA) automatically records your IP address, the time, the page requested and your browser type in server log files, to deliver the site and keep it secure (Art. 6(1)(f) GDPR). These entries are deleted after 30 days and are not used for analytics or advertising. See our Cookie Policy. The contact form processes the data you enter to answer your request (Art. 6(1)(b)/(f) GDPR).
If you submit a score in the optional Sky Dash mini-game, we transmit and store: a randomly generated device ID, the score, the platform (iOS/Android) and an optional player pseudonym (auto-generated, or chosen by you — letters/digits only, profanity-filtered on the device and on our server). No IP address is stored, and nothing links the score to your identity or your cycle data. Names are labels, not verified identities. Legal basis: legitimate interest (Art. 6(1)(f) GDPR — providing the game feature). You can reset the pseudonym at any time in the game.
Note on the store versions. MyDays X 5.0 in the App Store and on Google Play does not contain the AI assistant. The rest of this section, and every other mention of the “optional AI assistant” in this policy, applies only to test versions that still contain it; in those it is currently not reachable from the app’s menus.
The AI assistant answers general cycle questions. It is OFF until you explicitly agree in the app. When you ask a question, we transmit (with your explicit in-app consent): the text you typed and your cycle log — dates, cycle lengths, symptoms, measurements, moods, intimacy entries and your notes exactly as you wrote them (notes may mention other people). Photos and your name are never transmitted. Also sent: the app language and a random rate-limit ID. The question is processed by xAI Corp. (Grok) as a third-party AI provider under its own privacy policy (linked in the app before you consent). Do not include personal details in your questions; anything you type is transmitted as-is. Answers are general information, not medical advice. Nothing is stored linked to a person on our side. Legal basis: consent (Art. 6(1)(a) GDPR), revocable by simply not using the feature; the in-app opt-in can be reset by reinstalling or contacting us.
If you choose to share a product experience in the optional in-app community shelf (“What Worked For Me”), we transmit and store: the product name you type, your star rating and the symptom tags you pick — linked only to a one-way hash of a random app ID (one rating per product, updatable). The product name, an averaged star rating, the number of contributors and the most common tags are visible to other users of the app; your name, email, identity and your cycle data are never shared and cannot be derived. Product names are filtered on our server (no links, contact details or offensive terms), other users can report an entry, and reported entries are hidden pending review. Sharing is entirely optional and never rewarded. Legal basis: consent by the act of sharing (Art. 6(1)(a) GDPR); you can overwrite your own rating at any time or ask us to remove it.
If you enable Partner mode, selected calendar information and short notes are exchanged with your linked partner through our server. The content is end-to-end encrypted on your device before it is sent: our server only relays and temporarily stores encrypted data blobs together with a random pairing code — we cannot read the content, and it is not linked to your name or email. Either partner can end the link at any time in the app, which stops the exchange. Legal basis: consent by enabling the feature (Art. 6(1)(a) GDPR; for any health-related content you choose to share, Art. 9(2)(a) GDPR).
The in-app credit system (“MDX Credits”) keeps your credit balance on your device. To prevent duplicate reward grants and to support you on purchases, our server stores credit receipts (earn, purchase and spend events with amount and timestamp) linked only to a one-way hash of a random install identifier — never to your name, email or any cycle or health data. If you use the optional gifting feature, the server additionally stores the gift code, amount and the pseudonymous install hashes of sender and recipient so a code can be redeemed exactly once. Legal basis: performance of the feature you actively use (Art. 6(1)(b) GDPR) and our legitimate interest in fraud prevention (Art. 6(1)(f) GDPR). You can delete these records at any time (see section 7).
If you write to us through the in-app chat (“Message Christian”) or reply to an in-app card or question, the text you type is transmitted to and stored on our server. It is linked to the random install identifier of your app — not to your name or email unless you include them in the text yourself. In the reply log that identifier is kept only as a one-way hash; in your chat thread it is kept as such, so that an answer can reach your app. We use these messages solely to answer you and improve the app. Legal basis: consent by sending (Art. 6(1)(a) GDPR). You can delete your thread and replies at any time (see section 7).
How long I keep your chat, and how you delete it (from 18 October 2026): I keep a chat thread for 12 months after its last message — yours or mine, whichever is later. After that the thread is deleted automatically from my server, together with the reply address you may have saved in it, its nickname and notification markers and its internal key alias. You can also delete the whole conversation yourself at any time: in the app (from the October 2026 update on), open the chat, tap the “…” menu and choose “Delete conversation”. That removes the same set from my server immediately, including any card sentence that became part of the thread; it cannot be undone. The pseudonymous card tallies described below are not part of the thread and are not affected. Copies in my encrypted server backups are overwritten by the regular backup rotation, within six months at the latest. For a full erasure of everything linked to your install see section 7.
Daily cards with answer choices (since September 2026): when you tap a choice on a card, the card may ask a short follow-up question and offer a one-line text field — and it says right there, under the field, that your answer goes to Christian. Tapping alone sends nothing. Exactly one entry leaves your phone when you press Send or Skip (or close the card): the card’s id, the choice you tapped, the sentence you typed (if any), your app language and the random install identifier of your app. Tapped choices are stored as a pseudonymous tally (identifier one-way hashed). A typed sentence is read and answered by Christian, or on his behalf by his AI assistant (see 3.18), in your in-app chat thread (“Message Christian”), which is keyed to the same random install identifier — never to your name or email. Card answers are never combined with your cycle or health data and never shown to other users. You can skip or close every card without answering. Legal basis: consent by sending (Art. 6(1)(a) GDPR); deletion as above (see section 7).
When you write to us — by email, through the contact form, in the in-app chat (“Message Christian”), as a reply to an in-app card, or in the feedback form — Christian may use an AI assistant to read your message and to write or send the reply on his behalf. Every reply written by the AI assistant says so at the top, so you always know whether you are talking to a person or to an AI (transparency under Art. 50 of the EU AI Act). Decisions about refunds, deletion of your data, your subscription or anything else with a legal effect are always made by Christian personally.
What is transmitted: only the text of your message and the earlier messages of the same conversation. We remove email addresses from the text before it is sent. Your cycle log, backups, health-app data and payment data are never transmitted for this purpose.
Providers: Anthropic, PBC (USA) and xAI Corp. (USA) process the text as our processors. With both, data-processing agreements are in place that include the EU Standard Contractual Clauses (Art. 28 and Art. 46 GDPR). Under its commercial terms Anthropic may not use this content to train its models.
Legal basis: answering your request (Art. 6(1)(b) GDPR) and our legitimate interest in answering every message promptly (Art. 6(1)(f) GDPR). If you choose to include health details in your message, we process them because you sent them to us for this purpose after being informed here (Art. 9(2)(a) GDPR).
Your choice: write “human only” anywhere in your message and it is not passed to the AI assistant; Christian reads and answers it himself. You can object at any time (Art. 21 GDPR) by writing to info@mydaysx.club. For anything urgent, write to urgent@mydaysx.club.
If you use the dive log and tap the button that fetches conditions for a dive site, the app sends the dive-site name you typed and the coordinates it resolves to (rounded to about 11 metres) to Open-Meteo (open-meteo.com), a weather-data service. Nothing is sent unless you tap the button. No user ID, install ID, app version or cycle data is sent; the IP address of your device is necessarily visible to Open-Meteo. We do not store the result on our servers; it is saved in your dive log on your device. Legal basis: the feature you request, Art. 6(1)(b) GDPR.
If you use a MyDaysX home-screen widget with the Daily Hello feature, the app and the widget fetch our public content list and small cover pictures from our own server in the EU (aros.ai) over HTTPS. Article suggestions (CLAW MAG and I Am Enough) are switched on by default. MyDaysX Mag, “Friends & partners” and “Product tips” are off until you switch them on under Settings → Appearance → Widgets, and nothing is requested for a kind that is off. “Friends & partners” and “Product tips” are advertising: they are always marked “Ad”, offered from age 18 only, and never chosen from your cycle or health data. Our server sees your IP address, as with any request; no user ID, no cookies and no cycle or health data are sent, and your choice of kinds stays on your device. The ordinary web-server log of that server (IP address, time, requested file) is kept for about two weeks and then deleted. Legal basis: the widget feature you use, Art. 6(1)(b) GDPR, and for the optional kinds your choice to switch them on, Art. 6(1)(a) GDPR.
We use carefully selected providers; where required, data-processing agreements under Art. 28 GDPR are in place:
Our own servers are located in the EU. Where providers such as Google/AdMob or Apple process data outside the EU, this is based on appropriate safeguards (e.g. EU Standard Contractual Clauses or the EU-US Data Privacy Framework). For the optional AI assistant, the transmission of your question and cycle data to xAI Corp. (USA) is protected by appropriate safeguards — the EU Standard Contractual Clauses under our data-processing agreement with xAI (Art. 46 GDPR) — and, in addition, takes place only after your explicit consent given in the app before first use (Art. 49(1)(a) GDPR). For AI-assisted replies to your messages (see 3.18), the transfer of the message text to Anthropic, PBC and xAI Corp. (USA) is protected by the EU Standard Contractual Clauses in our data-processing agreements with them (Art. 46 GDPR).
Cycle data stored on your device remains until you delete it or uninstall the app. Older server backups remain available for a limited migration window, then are deleted. Anonymous statistics/diagnostics are kept only as long as needed for the stated purpose. Web-server log files of this website are deleted after 30 days; those of our app server after about two weeks. Otherwise we delete data when the purpose no longer applies and no statutory retention obligation prevents it.
Under the GDPR you have the following rights regarding your personal data:
In the app you can erase all your data directly (Settings → Privacy Dashboard → “Erase all my data”). To exercise any right, contact Server-side records (credit receipts, gift records, chat messages and card replies) can be deleted in the app as well (Settings → Privacy Dashboard → “Delete my data from our servers”) or via mydaysx.club/delete.info@mydaysx.club; we respond without undue delay and within one month (Art. 12(3) GDPR). Exercising your rights is free of charge.
Cycle predictions are simple estimates and do not produce legal or similarly significant effects within the meaning of Art. 22 GDPR. AI-assisted replies (see 3.18) only answer your message; they make no decisions with legal or similarly significant effect. The app is not a medical device and not a contraceptive.
The apps are intended for people aged 16 and older; you confirm your age during onboarding. In addition, the app may ask your operating system or app store for an age signal (Apple Declared Age Range on iOS 26 and later, Google Play Age Signals on Android) and uses it only to check whether you are under 16; if you decline to share it, your own entry governs. The app does not receive your exact birthdate from these services.
We use technical and organisational measures (HTTPS in transit, optionally encrypted backups, the app-lock password stored only as a salted hash). Absolute security of internet transmission cannot be guaranteed.
We may update this policy to reflect legal or feature changes. The current version is always available on this page.
Our detailed multilingual GDPR transparency document is available as a PDF (40+ languages), or on our Transparency Document page.
We do not sell your personal data. We disclose data only to the processors listed in section 4 (acting on our instructions), where required by law, or with your consent. Where we rely on legitimate interests (Art. 6(1)(f) GDPR) — e.g. for crash diagnostics, fraud prevention in the referral feature, and the basic operation and security of the service — our interest is to keep the apps stable, secure and improvable; we balance this against your rights and process only the minimum needed.
Providing your data is generally voluntary: cycle data is only processed if you choose to enter it, health-sync and research contributions are opt-in, and anonymous product analytics are on by default (you can opt out in Settings). Without certain data, related optional features may not work.
We do not sell your personal information, and we do not sell or share your health data. Categories we process are described in section 3 (identifiers such as a random install ID or your email if you subscribe; health information stored on your device; coarse anonymous usage data by default, which you can switch off). In the free version, advertising identifiers may be “shared” with Google AdMob for advertising as defined by California law. You can opt out: use the in-app Ad privacy options (where shown), limit ad tracking in your device settings, or remove ads entirely with Pro. California residents have the rights to know, correct, delete, port, to limit the use of sensitive personal information, and to non-discrimination for exercising these rights. Exercise them in-app (Settings → Privacy Dashboard) or via info@mydaysx.club. We honour authorized agents as provided by law.
This section serves as our Consumer Health Data Privacy Policy. Consumer health data we process: menstrual-cycle and related reproductive-health entries you create yourself in the app (see section 3.1) — collected directly from you, used solely to provide the tracking, prediction, backup, optional health-sync and optional AI-assistant features described above. We do not sell identifiable consumer health data. Properly de-identified, aggregate statistics (see section 3.5) are not consumer health data under these laws; we do not sell these aggregates either, we do not use them for advertising, and we do not share it with third parties except the processors listed in section 4 acting on our instructions (and, for the optional AI assistant, the anonymous summary described in section 3.13 with your consent). It stays on your device unless YOU trigger a transfer (backup, health sync, AI question). You may withdraw consent, access or delete your data at any time (in-app: Settings → Privacy Dashboard → “Erase all my data”, or email info@mydaysx.club); we respond within the timeframes required by the applicable law, and you may appeal a refusal by replying to our decision. We do not use geofencing around care facilities.