KnightDanny/ethiopian-calendar-overlay

Chrome extension that shows Ethiopian calendar dates inside Google Calendar, alongside the Gregorian dates, with Ethiopian public holidays highlighted in red. Amharic or Latin labels, exact Fasika computation via the Julian computus, and a tested Beyene-Kudlek date converter. Vanilla JavaScript, Manifest V3, zero dependencies. # 🗓️ Ethiopian Calendar Overlay for Google Calendar **A Chrome extension that shows Ethiopian calendar dates inside Google Calendar, right next to the Gregorian dates, and highlights Ethiopian public holidays in red.** Features · How It Works · Install · Holidays · Testing --- ## 📖 Overview Google Calendar has no built-in Ethiopian calendar support. This extension overlays it: every day cell gets a small label with its Ethiopian date (for example **ሰኔ 5**, with the year shown on the 1st of each Ethiopian month), while the Gregorian calendar stays exactly as it is. Ethiopian public holidays get a red wash, a red outline, and a bold red label with a tooltip naming the holiday. It is written in plain JavaScript with **zero dependencies and no build step**. It only reads the page DOM: no access to your Google account or calendar data, no network requests, and the only permission it asks for is `storage` (for its two settings). --- ## 🧱 Tech Stack | Layer | Technology | | ------------ | ---------------------------------------------------------------- | | Platform | Chrome Extension, Manifest V3 (works on Edge and Brave too) | | Language | Vanilla JavaScript (ES2017+), no frameworks, no build step | | Date math | Beyene-Kudlek algorithm via Julian Day Numbers | | Movable feasts | Julian computus (the reckoning used by the Ethiopian Orthodox Church) | | UI injection | Content script + `MutationObserver` | | Settings | `chrome.storage.sync` with a popup UI | | Tests | Plain Node.js asserts, `node test/convert.test.js` | --- ## ✨ Features - Ethiopian date label in every day cell of month view, plus week and day view headers - Labels in **Amharic** (መስከረም, ጥቅምት, ...) or **Latin transliteration** (Meskerem, Tikimt, ...), switchable from the popup - Ethiopian year shown on the 1 …