Data sources

Dates and legal status

Public-holiday dates for 100+ countries are pulled from Nager.Date, an open API that mirrors government gazettes and labour ministry calendars. Nager.Date does not include Islamic holidays (Ramadan, Eid al-Fitr, Eid al-Adha) or Jewish holidays (Rosh Hashanah, Yom Kippur, Passover, Hanukkah), because those follow the Hijri and Hebrew lunar calendars. Where we cover those holidays, the date is sourced separately from academic / religious calendars and we flag this in the brief.

Origins, customs, and controversies

The historical and cultural content is sourced from Wikipedia (cross-language where helpful), Encyclopedia Britannica, the Library of Congress, and - for the legal history of US federal holidays - the Office of Personnel Management. Every brief links the primary sources at the bottom of the page.

Limits we acknowledge

• Sub-national variation. A holiday may be a federal holiday in one country and a regional holiday in another. We flag this on each brief.
• Floating shops. Solar and lunar calendar drift means a fixed Gregorian date is only an approximation. We source from authoritative calendar tables.
• Cultural drift. Customs evolve faster than the underlying holiday. We try to cite recent sources when describing modern observance, and older sources when describing historical practice.
• Editorial bias. Where there is a contested framing, we present both with citations. We do not pretend neutrality on facts that have a single well-evidenced answer (e.g. the Holocaust happened, the Earth is round).

Citation policy

Every brief ends with a Sources section that links the primary reference for each non-trivial claim. If you spot a missing source or a citation that does not support the claim, please email us.