Fix Timezone Handling in Commit Timestamps for Consistent Time-of-Day Metrics

[nishtha-agarwal-211]

Description

Fixes #8964

Updated processCommitTimestamps in utils/dateHelpers.ts to extract hours using getAuthorLocalHour for ISO string inputs and getUTCHours() for Date objects, rather than relying on browser/system local date.getHours(). This ensures consistent, timezone-agnostic calculation of time-of-day metrics (morning, afternoon, evening, night) regardless of the execution environment or local machine's timezone setting.

Pillar

• 🎨 Pillar 1 — New Theme Design
• 📐 Pillar 2 — Geometric SVG Improvement
• 🕐 Pillar 3 — Timezone Logic Optimization
• 🛠️ Other (Bug fix, refactoring, docs)

Visual Preview

N/A (Backend utility logic & unit test optimization)

Checklist before requesting a review:

• I have read the CONTRIBUTING.md file.
• I have tested these changes locally (localhost:3000/api/streak?user=YOUR_USERNAME).
• I have run npm run format and npm run lint locally and resolved all errors (CI will fail otherwise).
• My commits follow the Conventional Commits format (e.g., feat(themes): ..., fix(calculate): ...).
• I have updated README.md if I added a new theme or URL parameter.
• I have started the repo.
• I have made sure that i have only one commit to merge in this PR.
• The SVG output matches the CommitPulse "premium quality" aesthetic standard (no raw elements, smooth animations, correct fonts).
• (Recommended) I joined the CommitPulse Discord community for contributor discussions, mentorship, and faster PR support.

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[retenta-bot]

This pull request addresses the issue of inconsistent timezone handling in commit timestamps, which is crucial for accurate time-of-day metrics. It builds on previous decisions to improve timezone logic and ensure consistent behavior across different environments. Notably, it aligns with the rationale behind the earlier decision to switch to getUTCHours() to prevent test failures in non-UTC timezones. Thank you for your contribution, and I look forward to your updates!

[Copilot]

Pull request overview

Updates CommitPulse’s date helper logic to make time-of-day metrics deterministic across environments by avoiding system-local timezone hour extraction for commit timestamps.

Changes:

• Adjust processCommitTimestamps to compute hours using getAuthorLocalHour for ISO strings and UTC hours for Date inputs.
• Update unit tests to use explicit UTC (Z) timestamps to prevent timezone-dependent failures.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
utils/dateHelpers.ts	Updates hour extraction in processCommitTimestamps to avoid relying on system-local timezone behavior.
utils/dateHelpers.test.ts	Normalizes test inputs to UTC (Z) timestamps and updates regression wording for timezone consistency.

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[github-actions]

📦 Next.js Bundle Size Report (Gzipped Sizes)

✨ No significant bundle size changes detected.

📊 Summary of Totals

Category	PR Size	Base Size	Difference
Total JS	5004.32 KB	5004.32 KB	0 B
Total CSS	354.80 KB	354.80 KB	0 B

[Aamod007]

Nice work untangling the timezone issues! Using \getAuthorLocalHour\ for ISO strings and \getUTCHours()\ for \Date\ objects in \processCommitTimestamps\ is a solid approach to ensure consistent bucketing regardless of the environment's timezone.

Re-adding the \Z\ (UTC identifier) to the test strings in \dateHelpers.test.ts\ properly aligns the test data with the new logic, ensuring that the regression test genuinely validates the timezone-agnostic behavior.

Labels applied:

• type:bug: Fixes inconsistent time-of-day metrics due to local timezone shifts.
• level:intermediate: Handles nuanced Date parsing and timezone-agnostic timestamp logic.
• quality:clean: The code accurately reflects the intent and the tests are properly updated.