Learnt from: Wasif-Shahzad
PR: #2593
File: holidays/calendars/islamic.py:3993-3994
Timestamp: 2025-06-04T10:09:28.732Z
Learning: In the holidays/calendars/islamic.py file, the Islamic calendar date methods in the _IslamicLunar class (like ali_al_rida_death_dates, ashura_dates, etc.) follow a consistent pattern of being single-line methods that return self._get_holiday(CONSTANT, year) without docstrings. New methods should follow this same pattern for consistency.

Learnt from: Wasif-Shahzad
PR: #2522
File: holidays/countries/yemen.py:158-163
Timestamp: 2025-05-06T13:01:22.693Z
Learning: In the holidays library, the RAMADAN_BEGINNING_DATES dictionary in country-specific Islamic holiday classes (like YemenIslamicHolidays) is used indirectly through the backend. When a country class calls _add_holiday_29_ramadan(), the IslamicHolidays implementation uses the country's custom calendar dates to calculate the 29th day of Ramadan by adding 28 days to the beginning date.

Learnt from: Wasif-Shahzad
PR: #2409
File: holidays/countries/qatar.py:27-46
Timestamp: 2025-04-03T16:58:27.175Z
Learning: In the holidays library, method names like _add_holiday_2nd_tue_of_feb() and _add_holiday_1st_sun_of_mar() use calendar constants internally through parent class implementations even when these constants don't appear directly in the file. Removing imports that seem unused based on a simple text search could break functionality.

Learnt from: KJhellico
PR: #2398
File: holidays/countries/guinea.py:101-106
Timestamp: 2025-04-03T13:03:16.558Z
Learning: For Islamic holidays in Guinea like "Lendemain de la nuit Lailatoul Qadr" (Day after Night of Power) and "Lendemain de la nuit du Maoloud" (Day after Prophet's Birthday), the naming refers to the daylight hours following the night when these Islamic observances occur. Since in the Islamic calendar days begin at sunset rather than midnight, methods like _add_laylat_al_qadr_day and _add_mawlid_day correctly calculate these dates without requiring an additional day offset in the implementation, following the same pattern as in the Ivory Coast implementation.

Learnt from: KJhellico
PR: #2398
File: holidays/countries/guinea.py:106-110
Timestamp: 2025-04-04T10:52:41.546Z
Learning: In the Guinea holidays implementation, observed Eid al-Fitr cases are covered by the test_eid_al_fitr_day() method, which tests both regular holiday dates and the observed dates when the holiday falls on a non-working day (for years >= 2023).

Learnt from: KJhellico
PR: #2398
File: holidays/countries/guinea.py:101-106
Timestamp: 2025-04-03T13:03:16.558Z
Learning: For Islamic holidays in Guinea like "Lendemain de la nuit Lailatoul Qadr" (Day after Night of Power) and "Lendemain de la nuit du Maoloud" (Day after Prophet's Birthday), the naming refers to the daylight hours following the night when these Islamic observances occur. Since in the Islamic calendar days begin at sunset rather than midnight, methods like _add_laylat_al_qadr_day and _add_mawlid_day correctly calculate these dates without requiring an additional day offset in the implementation.

Learnt from: KJhellico
PR: #2398
File: holidays/countries/guinea.py:106-110
Timestamp: 2025-04-04T10:52:41.546Z
Learning: In the Guinea holidays implementation, observed Eid al-Fitr cases are properly covered by the test_eid_al_fitr_day() method, which tests both the regular holiday dates and the observed dates when the holiday falls on a non-working day (for years >= 2023).

Learnt from: KJhellico
PR: #2386
File: holidays/countries/nepal.py:266-284
Timestamp: 2025-04-13T20:41:56.613Z
Learning: The Islamic holiday dates in the holidays library should only include officially verified dates, not predicted ones, to maintain accuracy. This is especially important for holidays that depend on lunar observations like Eid al-Fitr and Eid al-Adha.

Learnt from: KJhellico
PR: #2388
File: holidays/countries/ivory_coast.py:98-107
Timestamp: 2025-03-30T13:54:34.376Z
Learning: In the Islamic calendar, days begin at sunset rather than midnight. For holidays like "Lendemain de la Nuit du Destin" (Day after Night of Destiny) in Ivory Coast, the name refers to the daylight hours following the night of Laylat al-Qadr (27th of Ramadan). The implementation uses _add_laylat_al_qadr_day which correctly calculates this as the 27th day of Ramadan in the Gregorian calendar.

Learnt from: PPsyrius
PR: #2388
File: holidays/countries/ivory_coast.py:84-85
Timestamp: 2025-03-30T08:08:30.415Z
Learning: Islamic holiday logic should be implemented in the holidays/groups/islamic.py file, with country-specific files only calling these methods with the appropriate translated names.

Learnt from: Wasif-Shahzad
PR: #2409
File: holidays/countries/qatar.py:27-46
Timestamp: 2025-04-03T16:58:27.175Z
Learning: In the holidays library, method names like _add_holiday_2nd_tue_of_feb() and _add_holiday_1st_sun_of_mar() use calendar constants like FEB, TUE, MAR, and SUN internally through parent class implementations even when these constants don't appear directly in the file.

Learnt from: KJhellico
PR: #2465
File: holidays/countries/suriname.py:219-251
Timestamp: 2025-04-13T19:10:31.502Z
Learning: The _CustomIslamicHolidays classes in this project contain only exact verified holiday dates from reliable sources, rather than calculated or estimated future dates. This is by design to ensure accuracy, particularly for religious holidays that may follow lunar calendars or depend on local observations.

Learnt from: KJhellico
PR: #2614
File: holidays/countries/guyana.py:146-179
Timestamp: 2025-06-14T20:12:37.212Z
Learning: The _CustomHinduHolidays mechanism works through _CustomCalendarType metaclass which renames public attributes (like DIWALI_INDIA_DATES) with a postfix, allowing _HinduLunisolar::_get_holiday to find and use custom holiday dates. When _add_diwali_india() is called, it uses the custom dates if available rather than calculated dates.

Learnt from: KJhellico
PR: #2614
File: holidays/countries/guyana.py:146-179
Timestamp: 2025-06-14T20:12:37.212Z
Learning: The _CustomHinduHolidays mechanism works through _CustomCalendarType metaclass which renames public attributes (like DIWALI_INDIA_DATES) with a postfix, allowing _HinduLunisolar::_get_holiday to find and use custom holiday dates. When _add_diwali_india() is called, it uses the custom dates if available rather than calculated dates.

Learnt from: PPsyrius
PR: #2643
File: holidays/countries/mauritius.py:171-184
Timestamp: 2025-06-19T02:34:14.456Z
Learning: In the holidays library, _CustomIslamicHolidays subclasses follow a consistent pattern of NOT having docstrings. They go directly to defining date dictionaries, as evidenced by Malaysia, Singapore, UAE, and dozens of other country implementations.

Learnt from: PPsyrius
PR: #2354
File: holidays/countries/fiji.py:146-159
Timestamp: 2025-03-19T16:54:58.657Z
Learning: In the holidays library implementation, explicit holiday dates (like Diwali in Fiji) are only defined for historical years with official sources (2016-2025). Future dates beyond the explicitly defined range are automatically calculated by methods like _add_diwali, which provide approximations when official dates aren't yet available.

Learnt from: PPsyrius
PR: #2643
File: holidays/countries/mauritius.py:144-169
Timestamp: 2025-06-19T02:34:18.382Z
Learning: Custom holiday classes that extend _CustomHinduHolidays, _CustomIslamicHolidays, _CustomBuddhistHolidays, etc. in the holidays library do not use docstrings. They follow a pattern of using only inline comments above date dictionaries, as seen in Malaysia, Singapore, UAE, and other country implementations.