python-holidays Add Bhutan holidays

Proposed change

Add Bhutan holidays Resolves #1156.

Type of change

[x] New country/market holidays support (thank you!)
[ ] Supported country/market holidays update (calendar discrepancy fix, localization)
[ ] Existing code/documentation/test/process quality improvement (best practice, cleanup, refactoring, optimization)
[ ] Dependency update (version deprecation/pin/upgrade)
[ ] Bugfix (non-breaking change which fixes an issue)
[ ] Breaking change (a code change causing existing functionality to break)
[ ] New feature (new holidays functionality in general)

Checklist

[x] I've followed the contributing guidelines
[x] I've successfully run make check, all checks and tests are green

Jun 15 '25 17:06 Prateekshit73

Summary by CodeRabbit

New Features
- Added Bhutan as a supported country with comprehensive national and regional holiday coverage from 2007–2050, including major religious, royal, and cultural observances.
- Bhutan holidays now include both fixed and movable dates, supporting all districts and key local festivals.
- Bhutanese holidays are now available for lookup and calendar integration.
Documentation
- Updated README to reflect Bhutan as a newly supported country.
Tests
- Introduced extensive tests to verify Bhutanese holiday calculations and localization.
Chores
- Added new contributor "Aneesh Angane" to the contributors list.

Walkthrough

This change introduces comprehensive support for Bhutanese public holidays. It adds a Bhutan holiday provider, implements Tibetan lunisolar calendar logic, updates documentation and registry files, and includes new tests and data snapshots to verify correct holiday calculations for Bhutan from 1970 onward.

Changes

Cohort / File(s)	Change Summary
Bhutan holiday provider and Tibetan calendar logic `holidays/countries/bhutan.py`, `holidays/groups/tibetan.py`, `holidays/calendars/tibetan.py`	Added Bhutan holiday definitions and Tibetan lunisolar calendar classes with holiday date mappings and calculation methods.
Imports for Bhutan and Tibetan calendar `holidays/countries/__init__.py`, `holidays/groups/__init__.py`, `holidays/calendars/__init__.py`	Imported Bhutan country classes and Tibetan calendar classes to relevant modules.
Country registry update `holidays/registry.py`	Registered Bhutan with country codes "BT" and "BTN".
Documentation update `README.md`	Updated supported countries count and added Bhutan to the available countries list.
Tests for Bhutan and Tibetan calendar holidays `tests/countries/test_bhutan.py`, `tests/test_holiday_groups.py`	Added tests validating Bhutan holidays and Tibetan calendar holiday addition logic.
Holiday data snapshot `snapshots/countries/BT_COMMON.json`, `snapshots/countries/BT_15.json`, and multiple BT_*.json files	Added static JSON snapshots of Bhutan holidays from 2007 to 2050 for validation and reference.
Contributor acknowledgment `CONTRIBUTORS`	Added new contributor "Aneesh Angane" to the contributors list.

Estimated code review effort

Simple import and registry updates, README, CONTRIBUTORS: 🎯 1 (Trivial) | ⏱️ ~10 minutes
Bhutan country holiday provider and holiday group additions: 🎯 3 (Moderate) | ⏱️ ~90 minutes
Tibetan lunisolar calendar implementation (new calendar logic): 🎯 4 (Complex) | ⏱️ ~240 minutes
Tests for Bhutan and Tibetan calendar holidays: 🎯 2 (Simple) | ⏱️ ~45 minutes
Snapshot data file review: 🎯 1 (Trivial) | ⏱️ ~5 minutes

Overall estimated review effort: 🎯 3 (Moderate) | ⏱️ ~90 minutes

Assessment against linked issues

Objective	Addressed	Explanation
Add Bhutan holidays (#1156)	✅
Include major Bhutan public holidays and cultural observances (#1156)	✅
Use reliable sources such as Wikipedia and timeanddate.com for holiday data (#1156)	✅

Assessment against linked issues: Out-of-scope changes

No out-of-scope code changes detected. All changes align with the objectives related to adding Bhutan holidays.

Suggested reviewers

arkid15r
PPsyrius

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Jun 15 '25 17:06 coderabbitai[bot]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 100.00%. Comparing base (76bdfa6) to head (c3ee69b). :warning: Report is 87 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##               dev     #2635    +/-   ##
==========================================
  Coverage   100.00%   100.00%            
==========================================
  Files          273       276     +3     
  Lines        16309     16454   +145     
  Branches      2203      2203            
==========================================
+ Hits         16309     16454   +145

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Jun 15 '25 17:06 codecov[bot]

Can we rely on these sources :-

Jun 15 '25 17:06 Prateekshit73

List of Holidays 2024

List of Holidays (2025)

PHPA-II HOLIDAY LIST 2025

Holiday lists are useful, but what do linguistic researches provide us with?

Jun 16 '25 14:06 KJhellico

Thank you for your feedback regarding the sources I provided. I appreciate your emphasis on the importance of linguistic research in our work.

I have encountered some challenges in sourcing verified Dzongkha text. I found it difficult to extract proper Dzongkha text directly from these documents. For instance, when attempting to copy text from the official holiday list PDF, the Dzongkha characters did not transfer correctly, resulting in garbled output.

To ensure the integrity of our work, I am committed to using reliable and authoritative sources. If you have any specific suggestions for sources or methods to obtain verified Dzongkha text, I would greatly appreciate your guidance.

Thank you for your understanding.

Jun 17 '25 17:06 Prateekshit73

My comments on initial PR are still relevant.

Jun 29 '25 09:06 KJhellico

Should I remove localization support for dz_BT for now, as I was not able to find any official Dzongkha text?

Jun 29 '25 14:06 Prateekshit73

I think so, like with Nepal. I suggest focusing on the holidays themselves.

Jun 29 '25 14:06 KJhellico