package betacalendars

Beta Calendars for OCaml

Presentation-neutral Gregorian calendar structures for applications and temporal regression tests. This synchronous library models civil dates directly; it does not use timestamps or local time zones.

Why another calendar library?

calendar provides broad date/time functionality and calendars focuses on conversion among calendar systems. Beta Calendars focuses on deterministic month/year grids, bounded recurrence expansion, date ranges, boundary data, and fixtures for applications and tests.

Installation

opam install betacalendars

Quick start

open Betacalendars
let date = Civil_date.make ~year:2027 ~month:1 ~day:1
let grid = Month_grid.make ~year:2027 ~month:1
  ~first_weekday:Weekday.Monday ~layout:Month_grid.Fixed_six_weeks
  ~overflow:Month_grid.Adjacent_dates ()

Civil_date.make validates years 1–9999 and returns a structured result. add_days is timezone independent. Month grids expose rows of seven cells; fixed mode always returns 42 cells. Overflow cells either carry adjacent valid dates or None.

Year_grid.make returns January through December. Date_range is inclusive and provides iteration/fold before materializing lists. Recurrence.expand always requires a finite Date_range; it supports day intervals, weekdays, monthly/annual dates with explicit invalid-day policies, and ordinal/last weekdays. It is intentionally not a full RFC 5545 implementation.

Boundary.for_year and Fixture.year_turn_window produce deterministic structured values for regression tests. No API reads the clock, environment, network, or filesystem.

Compatibility and docs

The package targets OCaml 4.14 and later. API documentation is generated with odoc. See CONTRIBUTING.md, SECURITY.md, and CHANGES.md.

Project

Beta Calendars for OCaml is maintained as part of the Beta Calendars developer tooling project.

License

MIT. See LICENSE.