Why GitHub Actions Commits Don't Show on Your Contribution Graph — Fix with KST Timezone

After setting up automatic commits with GitHub Actions, I noticed something odd.

The commits were clearly there in the repository — but they weren't showing up on the contribution graph. Or they were showing up on the wrong date.

Commit list: April 26, 2026 — 2 commits  ✅
Graph:       April 26, 2026 — 1 commit   ❌ (one Actions commit missing)

Same day, same commits — so why was only one showing on the graph?

---

The Cause — UTC vs KST Timestamp Difference

GitHub uses the timezone offset in the commit timestamp to determine which day to credit for the contribution graph.

When I commit locally, my Mac's system timezone (KST) stamps the commit:

Local commit (KST 01:00):  2026-04-26 01:00:00 +0900  → Graph: April 26 ✅

GitHub Actions, on the other hand, runs on Ubuntu runners whose default timezone is UTC.

Actions commit (KST 00:00): 2026-04-25 15:00:00 +0000  → Graph: April 25 ❌

When Actions runs at KST midnight (00:00), UTC sees it as 15:00 the previous day. So even though the commit appears as April 26 in the commit list, the graph records it on April 25.

---

The Fix — export TZ='Asia/Seoul'

Set the timezone to KST before the git commit.

- name: Publish scheduled posts
  shell: bash
  run: |
    # ...

    if [ "$PUBLISHED" -gt 0 ]; then
      export TZ='Asia/Seoul'          # ← add this one line
      git config user.name "your-name"
      git config user.email "your@email.com"
      git add ...
      git commit -m "..."
      git push
    fi

After this, the commit timestamp looks like:

2026-04-26 00:05:32 +0900  → Graph: April 26 ✅

Everything executed after the export TZ declaration runs in KST, so both the author date and committer date on the git commit get the +0900 offset.

---

Full Workflow Example

name: Publish Scheduled Posts

on:
  schedule:
    - cron: '5 15 * * *'  # daily at 00:05 KST (= 15:05 UTC)
  workflow_dispatch:

jobs:
  publish:
    runs-on: ubuntu-latest
    permissions:
      contents: write

    steps:
      - uses: actions/checkout@v4

      - name: Publish scheduled posts
        shell: bash
        run: |
          TODAY=$(TZ='Asia/Seoul' date '+%Y-%m-%d')
          PUBLISHED=0

          for file in content/scheduled/*.md; do
            [ -f "$file" ] || continue
            # ... date check logic ...
            mv "$file" "content/posts/$(basename $file)"
            PUBLISHED=$((PUBLISHED + 1))
          done

          if [ "$PUBLISHED" -gt 0 ]; then
            export TZ='Asia/Seoul'
            git config user.name "your-name"
            git config user.email "your@email.com"
            git add content/posts/ content/scheduled/
            git commit -m "post: publish $PUBLISHED scheduled post(s) ($TODAY)"
            git pull --rebase origin main
            git push
          fi

---

Key Settings

Setting	Value	Why
cron	5 15 * * *	UTC 15:05 = KST 00:05
TODAY variable	TZ='Asia/Seoul' date	Compute publish date in KST
git commit	export TZ='Asia/Seoul'	Stamp commit timestamp in KST
user.email	Your GitHub email	Required for graph to count it

---

Troubleshooting

Email is correct but commits aren't showing on the graph

If TZ isn't set and commits are stamped in UTC, the date shifts by one day. Confirm that export TZ='Asia/Seoul' comes before git config.

Commits exist but appear on the wrong date

The GitHub contribution graph has a cache. It typically updates within minutes to a few hours. If it's not reflected immediately, wait a bit before worrying.

Checking contribution requirements

Three conditions must all be met for a commit to count on the GitHub contribution graph:

1. The commit's author email must be registered and verified on the GitHub account
2. The commit must be on the default branch (main)
3. The repo must not be a fork

---

Summary — The Core Flow

Problem:
  Actions runner is in UTC timezone
  → KST midnight commit is stamped as the previous day in UTC
  → Shows up one day early on the contribution graph

Fix:
  Add export TZ='Asia/Seoul' before git commit
  → Commit timestamp gets +0900 suffix
  → GitHub reads it as the KST date
  → Contribution graph is accurate ✅

It's a one-line change — export TZ='Asia/Seoul' — but seeing the green squares land on the right days feels surprisingly satisfying.