> For clean Markdown content of this page, append .md to this URL. For the complete documentation index, see https://buildwithfern.com/learn/llms.txt.

# Auto-update last updated dates

> Use a GitHub Action to automatically update the last-updated frontmatter property when MDX files change.

You can use a GitHub Action to automatically update the [`last-updated` frontmatter property](/learn/docs/configuration/page-level-settings#last-updated) whenever MDX files are modified in a pull request. This keeps your documentation's "Last updated" timestamp accurate without manual updates.

## Set up the workflow

When a pull request is opened or updated, the workflow detects which MDX files changed, updates or adds a `last-updated` field in their frontmatter with the current date, and commits the changes back to the PR branch. That stamp commit is itself a `synchronize` event, so the workflow runs a second time on its own commit; the second run stamps the same date, finds no diff, and exits without committing.

#### Create a token

Give the workflow a personal access token to push its stamp commit with. A push authenticated this way triggers the PR's other workflows the same way a human push does, so `fern check` and preview deploys run automatically.

1. Under **Settings > Developer settings > Personal access tokens**, create a fine-grained token scoped to your docs repository with **Contents: Read and write**. Classic tokens with the `repo` scope also work.

2. Add it under **Settings > Secrets and variables > Actions** as `DOCS_BOT_TOKEN`. A token your repository already uses for release or sync automation works too, as does a [GitHub App installation token](https://github.com/actions/create-github-app-token), which avoids per-user expiry on team-maintained repositories.

If your repository runs no other checks on docs PRs, you can skip adding the secret and use the built-in `GITHUB_TOKEN` instead. GitHub holds every `pull_request` run the stamp push triggers behind an **Approve workflows to run** banner until someone with write access approves it, and no repository or organization setting turns this off.

#### Add the workflow

Add this workflow to your documentation repository, with `token` set to the secret you created. It stamps dates in "Month Day, Year" format (e.g., "December 11, 2025"); change the `date` command to use a different format.

**`.github/workflows/update-last-updated.yml`**

```yml title=".github/workflows/update-last-updated.yml" maxLines=14
name: Update last updated date

# Trigger this workflow when PRs are opened or updated
on:
  pull_request:
    types: [opened, synchronize]
    branches:
      - main  # Adjust to match your main branch name

jobs:
  update-last-updated:
    runs-on: ubuntu-latest
    # No token can push to a contributor's fork, so the push would fail.
    # Skip fork PRs instead.
    if: github.event.pull_request.head.repo.full_name == github.repository
    permissions:
      contents: write         # Required to commit changes
      pull-requests: write    # Required to update the PR
    steps:
      # Step 1: Check out the PR branch
      - name: Checkout repository
        uses: actions/checkout@v4
        with:
          ref: ${{ github.head_ref }}  # Check out the PR's source branch
          fetch-depth: 0
          token: ${{ secrets.DOCS_BOT_TOKEN }}  # A PAT, not GITHUB_TOKEN

      # Step 2: Identify which MDX files changed in this PR
      - name: Get changed MDX files
        id: changed-files
        uses: tj-actions/changed-files@v45
        with:
          files: |
            **/*.mdx  # Only track changes to .mdx files

      # Step 3: Update the last-updated field in each changed MDX file
      - name: Update last-updated frontmatter
        if: steps.changed-files.outputs.any_changed == 'true'
        run: |
          # Generate current date in "Month Day, Year" format (e.g., "December 11, 2025")
          # Modify the date format here if you prefer a different style
          CURRENT_DATE=$(date +"%B %-d, %Y")
          echo "Current date: $CURRENT_DATE"

          # Process each changed MDX file
          for file in ${{ steps.changed-files.outputs.all_changed_files }}; do
            echo "Processing: $file"

            # Skip if file was deleted or doesn't exist
            if [ ! -f "$file" ]; then
              echo "File not found, skipping: $file"
              continue
            fi

            # Check if file has frontmatter (must start with ---)
            if ! head -1 "$file" | grep -q "^---"; then
              echo "No frontmatter found, skipping: $file"
              continue
            # If file already has a last-updated field, update it
            elif grep -q "^last-updated:" "$file"; then
              echo "Updating existing last-updated field"
              sed -i "s/^last-updated:.*$/last-updated: $CURRENT_DATE/" "$file"
            # If file has frontmatter but no last-updated field, add it
            else
              echo "Adding last-updated field to existing frontmatter"
              # This awk command inserts the last-updated field just before the closing ---
              awk -v date="$CURRENT_DATE" '
                BEGIN { in_frontmatter=0; added=0 }
                NR==1 && /^---$/ { in_frontmatter=1; print; next }
                in_frontmatter && /^---$/ && !added { print "last-updated: " date; added=1; print; in_frontmatter=0; next }
                { print }
              ' "$file" > "${file}.tmp" && mv "${file}.tmp" "$file"
            fi
          done

      # Step 4: Commit and push the updated files back to the PR
      - name: Commit changes
        if: steps.changed-files.outputs.any_changed == 'true'
        run: |
          git config --local user.email "github-actions[bot]@users.noreply.github.com"
          git config --local user.name "github-actions[bot]"
          git add -A
          # Only commit if there are actual changes
          if git diff --staged --quiet; then
            echo "No changes to commit"
          else
            git commit -m "chore: update last-updated date in MDX files"
            git push
          fi
```

## Skip specific pull requests

Stamping every touched page is wrong for a bulk change: a backfill or a sync PR that touches hundreds of pages would rewrite every date to the merge date. Gate the job on a label to opt those PRs out:

```yml
jobs:
  update-last-updated:
    if: ${{ !contains(github.event.pull_request.labels.*.name, 'skip-last-updated') && github.event.pull_request.head.repo.full_name == github.repository }}
```

> Use a GitHub Action to automatically update the last-updated frontmatter property when MDX files change.