diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 8847192..ea994c0 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -4,27 +4,27 @@
 
 ### Versioning
 
-This project follows [Semantic Versioning](https://semver.org/). Git tags are always `v`-prefixed (e.g. `v1.2.3`). Pre-release tags use the format `v1.2.3-rc.1`.
+This project follows [Calendar Versioning](https://calver.org/) using a `YY.M.PATCH` scheme (e.g. `v26.8.0`), a SemVer-compatible variant of CalVer. npm requires `package.json` versions to be valid [SemVer](https://semver.org/), which disallows leading zeros in numeric identifiers, so `YY` is the last two digits of the year as a non-zero-padded number (e.g. `26` for 2026), `M` is the non-zero-padded month, and `PATCH` resets to `0` for the first release of a given year/month and increments for subsequent releases within that same month. Git tags are always `v`-prefixed (e.g. `v26.8.0`). Pre-release tags use the format `v26.8.0-rc.1`.
 
-| Change type                       | Example               |
-| --------------------------------- | --------------------- |
-| Bug fix (patch)                   | `v0.0.17` → `v0.0.18` |
-| New feature, non-breaking (minor) | `v0.0.17` → `v0.1.0`  |
-| Breaking change (major)           | `v0.1.0` → `v1.0.0`   |
+| Change type                                | Example               |
+| ------------------------------------------- | --------------------- |
+| Another release in the same month           | `v26.8.0` → `v26.8.1` |
+| First release in a new month (same year)    | `v26.8.1` → `v26.9.0` |
+| First release in a new year                 | `v26.9.0` → `v27.1.0` |
 
-Use an `rc` pre-release tag (e.g. `v1.2.3-rc.1`) before promoting to a stable release.
+Use an `rc` pre-release tag (e.g. `v26.8.0-rc.1`) before promoting to a stable release.
 
 ### Steps
 
 1. Bump the version in `package.json`.
 2. Commit the version bump and open a PR against `main`.
-3. Once merged, tag the release, replacing `vX.Y.Z` with the version from `package.json`:
+3. Once merged, tag the release, replacing `vYY.M.PATCH` with the version from `package.json`. Pass `-m` so `git tag -a` doesn't open an editor:
    ```sh
-   git tag vX.Y.Z
-   git push origin vX.Y.Z
+   git tag -a vYY.M.PATCH -m "vYY.M.PATCH"
+   git push origin vYY.M.PATCH
    ```
 
 Pushing the tag triggers the release workflow automatically:
 
-- **Stable releases** (e.g. `v1.2.3`): publishes to npm and creates a GitHub release.
-- **Release candidates** (e.g. `v1.2.3-rc.1`): publishes to npm under the `rc` dist-tag only.
+- **Stable releases** (e.g. `v26.8.0`): publishes to npm and creates a GitHub release.
+- **Release candidates** (e.g. `v26.8.0-rc.1`): publishes to npm under the `rc` dist-tag only.