HolidayOps — Working Days API

2026 · Full-stack · Django + React · API platform

Every working day, in every country.

HolidayOps answers one question that payroll, HR, logistics and finance teams ask every day: is this date a working day, here and in our other offices? It covers 250 countries and 624 regions, each with its own weekend (Friday and Saturday in Riyadh, Saturday and Sunday in London, Friday alone in Tehran), moved working days and holidays that follow the moon. Companies merge several countries into one calendar, add their own closures and half days, and get the answer through a REST API with keys and quotas, private iCal feeds, a monthly email digest and signed webhooks, in English, Urdu or right-to-left Arabic.

Source Case study

Home — live answers and a calendar that turns with the month

250
countries: 624
regions: 481
automated tests: 3
languages, RTL

Built in October 2026 across 43 pull requests: a pure-Python domain layer on the open-source holidays library with 100% branch coverage, Django REST Framework on MySQL and Redis, Celery for feeds, digests and webhooks, and a React web app with a three.js globe on the sign-in pages. The public site is server-rendered with no JavaScript at all: a landing page that shows which countries are off right now, a page per country and year, a 'who is off today' page, an embeddable widget and a working-day overlap tool. Accounts have two-factor sign-in, Google and Microsoft sign-in, emailed reset codes and self-serve data export and deletion. 447 backend and 34 frontend tests run on every pull request.

01
The weekend is data, not an assumption: every answer uses the country's own weekend rules, including countries that changed them, and a company calendar can override them.
02
One engine behind everything: the API, the iCal feeds, the digests, the webhooks and the public pages all ask the same small domain layer, so they can never disagree about a date.
03
Live, without JavaScript: the landing page and the 'who is off today' page put all 250 countries on their own local date, rebuilt every hour, and still render as plain HTML.
04
Security by default: hashed keys and feed tokens, tenant isolation tested on every endpoint, a DNS-rebinding-proof SSRF guard for webhooks, one-time reset codes and replay-proof two-factor codes.

Screens · HolidayOps