Parse Unix Timestamps in CI/CD Log Analysis Workflows

Deployment log:
[1709800400] Starting deployment pipeline
[1709800423] Building Docker image
[1709800891] Pushing to registry (took 468s ??)
[1709800912] Deploying to production cluster
[1709800945] Health checks passed
[1709800950] Deployment complete

# What time did this actually happen?
# How long did the Docker push take?
# Was this during business hours?

name: Deploy with Timeline
on:
  push:
    branches: [main]

jobs:
  deploy:
    runs-on: ubuntu-latest
    steps:
      - name: Record deployment start
        run: |
          START_TS=$(date +%s)
          START_HUMAN=$(date -u '+%Y-%m-%d %H:%M:%S UTC')
          echo "START_TS=$START_TS" >> $GITHUB_ENV
          echo "START_HUMAN=$START_HUMAN" >> $GITHUB_ENV
          echo "🚀 Deployment started at $START_HUMAN"

      - name: Build and push Docker image
        run: |
          PUSH_START=$(date +%s)
          docker build -t myapp:${{ github.sha }} .
          docker push myapp:${{ github.sha }}
          PUSH_DURATION=$(($(date +%s) - PUSH_START))
          echo "PUSH_DURATION=${PUSH_DURATION}s" >> $GITHUB_ENV
          echo "Docker push took ${PUSH_DURATION}s"

      - name: Deploy to production
        run: kubectl set image deployment/myapp app=myapp:${{ github.sha }}

      - name: Generate deployment timeline
        if: always()
        run: |
          END_TS=$(date +%s)
          TOTAL=$((END_TS - $START_TS))
          END_HUMAN=$(date -u '+%Y-%m-%d %H:%M:%S UTC')

          cat > /tmp/timeline.md << EOF
          ## 📋 Deployment Timeline

          | Event | Time (UTC) | Duration |
          |-------|-----------|----------|
          | Started | $START_HUMAN | — |
          | Docker push | — | $PUSH_DURATION |
          | Completed | $END_HUMAN | ${TOTAL}s total |

          **Commit:** ${{ github.sha }}
          **Triggered by:** ${{ github.actor }}
          EOF

          cat /tmp/timeline.md

      - name: Post timeline to PR
        if: github.event_name == 'pull_request'
        run: gh pr comment ${{ github.event.pull_request.number }} --body-file /tmp/timeline.md
        env:
          GH_TOKEN: ${{ secrets.GITHUB_TOKEN }}