Treemoon: Ogham Tree Calendar
The ancient Irish alphabet
Only for iPhone
Free · In‑App Purchases · Designed for iPhone. Not verified for macOS.
iPhone
December 23rd belongs to none of the thirteen trees. Treemoon leaves that day standing rather than tidying it away.
Ogham is a real writing system. It was cut into stone in Ireland and Britain between the fourth and sixth centuries, and several hundred of those inscriptions still stand today. Treemoon lays out all twenty letters one by one, and reads the thirteen-month tree calendar that grew up around the trees those letters are named for.
■ The twenty staves
Every stave in the alphabet. The Irish letter name, its sound value, how the strokes are cut against the stem line, which aicme (group of five) it belongs to, and the tree it carries. The glyphs are drawn as vectors rather than set in a Unicode font, so the stem and the strokes render correctly on any device. The whole chart is free.
■ The tree calendar
A year divided into thirteen tree months. For each tree: the Irish name and the botanical name, the span of days it governs, its element and its symbols. Enter a date and the app tells you which tree month it falls in. December 23rd belongs to none of the thirteen — it is the Nameless Day, and we left it there rather than rounding it away.
■ Said plainly
Ogham is genuinely ancient. The thirteen-month tree calendar is not. It is not a druid calendar; it was assembled in the middle of the twentieth century and spread through the modern Celtic revival. We did not hide that to make the app look older than it is — there is a page inside the app about nothing else.
Every line of commentary was written from scratch. Nothing is copied or translated from any book or website.
■ Drawing a stave, and keeping notes
Write down a question, shake the phone, and one letter comes out of the bag. Read its keywords and its commentary, then write down what you were actually thinking that day. It is there for entertainment and reflection.
■ Widgets
Home screen and lock screen: today's tree and its letter, without opening the app.
■ Completely offline
There is no networking code in this app at all. No account, no login, no analytics. The date you enter and the notes you write stay on this device. Everything works in airplane mode.
■ Paying
No subscriptions. One lifetime unlock opens everything. The free tier covers the full twenty-letter chart, the whole tree calendar, the tree of the day, one draw a day, and the small widget.
Treemoon is a cultural and language reference with a reflective side. It does not predict anything, and it is not a substitute for medical, legal or financial advice.
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The developer, Byoungho Kim, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Collected
The developer does not collect any data from this app.
Accessibility
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Information
- Seller
- Byoungho Kim
- Size
- 2.3 MB
- Category
- Reference
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Vision
Requires visionOS 1.0 or later.
- iPhone
- Languages
English and 3 more
- English, Japanese, Korean, Simplified Chinese
- Age Rating
9+
- 9+
- Infrequent
Mature or Suggestive Themes
- In-App Purchases
Yes
- Treemoon Pro $5.99
- Copyright
- © 2026 blue-code
