#scheduling

Expand and describe RFC 5545 recurrence rules — the RRULE that powers calendar repeats. The expand endpoint takes an RRULE and a start date-time and returns the next occurrence dates, correctly handling FREQ (daily, weekly, monthly, yearly and the finer hourly/minutely/secondly), INTERVAL (every 2 weeks…), COUNT and UNTIL, BYDAY including ordinals like 2MO or -1FR (so "the last Friday of the month" or "the third Sunday of June"), BYMONTHDAY including negatives (-1 for the last day of the month), BYMONTH and WKST. The describe endpoint turns a rule into a plain-English sentence such as "every week on Monday, Wednesday and Friday, 10 times". Everything is computed locally in UTC and deterministically, so it is instant, private and identical on every machine. Ideal for scheduling and booking systems, calendar and reminder apps, billing and subscription cycles, job and report scheduling, and showing customers when something next happens. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This expands the recurrence rule; to build a downloadable .ics calendar event use an iCalendar API, and for plain date arithmetic use a date-time API.

api.oanor.com/rrule-api

Generate tournament schedules — entirely locally. The roundrobin endpoint builds a full round-robin fixture list in which every participant plays every other exactly once, or twice (home and away) with double=true, using the classic circle method: it balances home and away across the rounds and, when there is an odd number of entrants, automatically gives each a bye in turn. The bracket endpoint builds a single-elimination knockout bracket: it rounds the field up to the next power of two, seeds the entrants in standard bracket order so the top seed meets the lowest and the strongest only meet in later rounds, awards the byes to the highest seeds, and lays out every round through the Final with the right names (Quarterfinal, Semifinal, Final). Pass a list of team or player names, or simply a number of participants. Everything is computed locally and deterministically, so it is instant and private. Ideal for sports leagues and apps, esports and gaming ladders, club and school competitions, hackathons and any event that needs fair fixtures. Pure local computation — no key, no third-party service, instant. Live, nothing stored. 3 endpoints. This generates the schedule; for live scores, results and real-world fixtures use a sports data API.

api.oanor.com/tournament-api

Build a valid RFC 5545 iCalendar (.ics) event from simple parameters — and get ready-to-use "add to calendar" links for Google, Outlook, Office 365 and Yahoo. Pass a title, start and end (ISO 8601 or unix timestamps, in UTC) — or a duration in minutes, or an all-day flag — plus optional location, description, URL, organizer, an RRULE recurrence (e.g. FREQ=WEEKLY) and a reminder (a VALARM N minutes before). The service returns the fully-formed .ics text with correct escaping and 75-octet line folding, a base64 data: URI you can drop straight into a download link, and the four calendar deep-links. A second endpoint parses raw .ics text back into structured JSON events. Everything is computed locally with no network calls, so it is fast and deterministic. Built for booking and scheduling flows, event pages, email "add to calendar" buttons, reminders and no-code automations. A calendar-event builder — distinct from date/time math (datetime), public-holiday data (holidays) and the Jewish calendar (hebcal). No upstream key, no cache.

api.oanor.com/ical-api

Public holidays for 120+ countries — by year, the next upcoming holidays for a country, and the list of supported countries. Each holiday includes the date, English and local name, scope (national/regional) and type. Ideal for HR, scheduling and booking systems.

api.oanor.com/holidays-api