[Bug]: Fix streak calculation by using user timezone instead of UTC dates

[kunal-yelgate]

GitHub records contribution activity using UTC timestamps, while RankerHub users view activity according to their local timezone.

Example

• User Timezone: Asia/Kolkata (UTC+5:30)
• Contribution Time: 11:55 PM (Local Time)
• GitHub Timestamp: 06:25 PM UTC

When streak calculations use UTC dates directly, contributions may be attributed to a different calendar day than the user expects, causing valid streaks to appear broken.

Changes

• Store and use the user's timezone during streak calculations.
• Convert GitHub contribution timestamps to the user's local timezone before evaluating daily activity.
• Base streak validation on local calendar days instead of raw UTC dates.
• Add test coverage for timezone conversions and day-boundary edge cases.

Impact

Before

• Users could lose streaks incorrectly.
• Daily contribution counts could be inaccurate.
• Users outside UTC were disproportionately affected.

After

• Streak calculations respect the user's local timezone.
• Contributions near midnight are assigned to the correct local day.
• Streaks remain consistent with GitHub contribution activity.
• Improved accuracy and trust in contribution tracking.

Acceptance Criteria

• Streak calculations use the user's local timezone.
• Contributions near midnight are assigned to the correct local day.
• Streaks remain consistent with GitHub contribution activity.
• Tests added for timezone and day-boundary scenarios.

Fixes

Fixes #505

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Project	Deployment	Actions	Updated (UTC)
ranker-hub	Ready	Preview, Comment	Jun 15, 2026 9:32am

[kunal-yelgate]

Hey @indresh404 review the PR