feat: Add getLastDayOfMonth utility with tests

[jhechtf]

Summary by CodeRabbit

• Tests

  • Expanded test coverage for date utility functions, including validation of leap-year and non-leap-year behavior.

• New Features

  • Added a date calculation utility to support improved date handling across the application.

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Project	Deployment	Actions	Updated (UTC)
bill-tracker-mono	Ready	Preview, Comment	Apr 5, 2026 8:02am

[coderabbitai]

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between ce82925 and c72ee4d.

📒 Files selected for processing (2)

• apps/website/src/lib/util/date.test.ts
• apps/website/src/lib/util/date.ts

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Walkthrough

A new utility function getLastDayOfMonth is added to the date utilities module to compute the final day of any given month, accounting for varying month lengths and leap years. Accompanying test cases verify correct behavior for both leap-year and non-leap-year scenarios.

Changes

Cohort / File(s)	Summary
Date Utility Enhancement apps/website/src/lib/util/date.ts, apps/website/src/lib/util/date.test.ts	Added new getLastDayOfMonth function that clones a date, advances one month, and rolls back to the last day of the original month. Updated test imports and added comprehensive test cases covering leap-year (29) and non-leap-year (28) February behavior.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~8 minutes

Poem

🐰 A calendar's helper, so neat and so fine,
Counts the last day of each month in line!
February twists, leap or not so,
Our fuzzy friend's logic helps dates truly flow! 📅✨

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/date-utils

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[jhechtf]

• fix: Payments page with history navigation, month filter, and progress bar #140
• feat: Add getLastDayOfMonth utility with tests #139 👈 (View in Graphite)
• feat: Add progress, tooltip, and floating attachment components #138
• feat: begin move to remote functions #133 : 4 other dependent PRs (#134 , #135 , #136 and 1 other)
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[jhechtf]

Merge activity

• Apr 5, 7:58 AM UTC: A user started a stack merge that includes this pull request via Graphite.
• Apr 5, 8:01 AM UTC: Graphite rebased this pull request as part of a merge.
• Apr 5, 8:02 AM UTC: @jhechtf merged this pull request with Graphite.