Privacy policy

Last updated: 23 September 2026

Chengyu Calendar teaches you a new Chinese idiom every day. It was built to use as little of your data as possible, and this policy explains exactly what that means. The app is made by one person: me, Fiachra (Fiki) MacFadden.

In short

There is no account to create and no sign-in, and the app contains no analytics, advertising or tracking code of any kind. Your settings are stored on your iPhone and never leave it. Apple handles all payments, and a service called RevenueCat checks whether your subscription is active; it never learns your name, email address or Apple ID. If you email me, I see what you send.

What stays on your iPhone

The app stores your settings, such as your choice of Simplified or Traditional characters, and the content the widget shows. These stay on your phone and are never sent to me or anyone else. While the app is open, it uses your phone’s motion sensor for a visual effect; these readings are never saved or sent. Deleting the app deletes everything it stored.

Subscriptions

Chengyu Calendar is a subscription, sold through Apple’s App Store. Apple takes your payment, so I never see your card details, your name or your Apple ID. Apple’s own privacy policy is at apple.com/legal/privacy.

To check that your subscription is active, the app uses RevenueCat, a company that verifies App Store purchases for me. RevenueCat receives a random ID for your copy of the app, not connected to your name, email address or Apple ID; your purchase record, meaning which plan you chose, its price, your App Store country, and when it started and renewed; and basic technical details, meaning your app and iOS versions, your iPhone model, and your IP address, which every internet connection shares.

I use this to give you the subscription you paid for, and to see overall numbers, such as how many people subscribe to each plan and in which countries.

RevenueCat stores this data in the United States. It handles the data only on my behalf, under standard contract terms that include the protections data protection law requires for data sent abroad. RevenueCat’s privacy policy is at revenuecat.com/privacy.

What Apple tells me

Apple gives every App Store developer reports on downloads, sales and subscriptions. They show totals by country, date, plan and price. If you have agreed to share analytics with developers in your iPhone’s settings, Apple may also send me overall usage figures and anonymous crash reports. None of these reports identify you.

Emailing me

Tapping Contact on the back of the calendar opens a new email to me in your mail app. The email already includes the app’s version, your iOS version and your iPhone model, to help me solve your problem. You can see and delete any of this before you send it. I receive your email address and whatever you write. I use it only to reply and to fix what you report, and I delete it once it is no longer needed.

Sharing

I never sell data or share it for advertising. The only other companies involved are Apple and RevenueCat, as described above.

How long data is kept

Your purchase record is kept while your subscription is active, and afterwards only as long as accounting and tax law require. Emails are deleted once they are no longer needed. Everything else stays on your phone until you delete the app.

Keeping data safe

Data sent between the app, Apple and RevenueCat is always encrypted, and access to it is protected. No system is perfectly secure, but I keep what I hold to a minimum, so there is very little to protect.

Children

Chengyu Calendar is suitable for all ages. Apart from the subscription check described above, it collects no data from anyone, children included.

Your rights

Wherever you live, you can ask me to show, correct or delete any personal data I hold about you. If you live in the EU or the UK, the law also gives you the right to download your data and to object to how it is used.

I hold almost nothing about you, so there is usually nothing to act on. Everything the app stores is on your phone, and deleting the app deletes it. To have RevenueCat’s record of your purchase deleted, email me the order ID from Apple’s receipt email, so I can find it.

I handle your purchase record because it is needed to provide your subscription, and your emails because it is in my legitimate interest to answer them.

If you are unhappy with how your data is handled, please write to me first. You also have the right to complain to the data protection authority where you live.

Changes

If this policy changes, I will update this page and the date at the top. I will also mention important changes in the app’s release notes.

Contact

Chengyu Calendar is made by Fiachra (Fiki) MacFadden. For anything about this policy, or about the app and its Home Screen widget, email fiki@zhiyin.dev.