Quando

Quando calculates availability and deadlines from recurring rules and exceptions. Use schedules for opening hours, rotas for assignments, and tallies for numeric contributions over time.

npm install @kensio/quando

Quando uses the standard Temporal API. If your runtime needs a polyfill, follow the installation steps before running the examples.

Start with a schedule

import { schedule, weekdays } from "@kensio/quando";

const openingHours = schedule({ zone: "Europe/London" })
  .open(weekdays(), "09:00-17:00")
  .closed("2026-12-25")
  .setHours("2026-12-24", "09:00-15:00");

This schedule opens Monday to Friday from 09:00 to 17:00. It closes on Christmas Day and replaces Christmas Eve’s hours with 09:00 to 15:00. Later calls override earlier ones for the periods they select.

Ask schedule questions

const placed = Temporal.ZonedDateTime.from(
  "2026-03-13T16:55[Europe/London]",
);

openingHours.isOpen(placed);
// true

openingHours.nextOpenInterval(placed.add({ hours: 2 }))?.start?.toString();
// 2026-03-16T09:00:00+00:00[Europe/London]

openingHours
  .addOpenTime(placed, Temporal.Duration.from({ hours: 3 }))
  ?.toString();
// 2026-03-16T11:55:00+00:00[Europe/London]

At 16:55 on Friday, the office is open for five more minutes. The next opening after Friday evening is Monday at 09:00. Adding three open hours uses the remaining Friday minutes and finishes on Monday at 11:55.

The schedule API also measures open time within a date range.

Choose an API

API	Use it for
schedule	Opening hours and other open or closed periods
rota	Assigning names or application values over time
tally	Adding numeric values where periods overlap
Rules	Composing custom definitions of when

All three APIs use rules to select the periods they cover.

Store definitions

Quando definitions are JSON-compatible data. Parsers validate stored data and restore the API methods.

import { parseSchedule } from "@kensio/quando";

const stored = JSON.stringify(openingHours);
const restored = parseSchedule(JSON.parse(stored));

Continue reading

The getting-started guide builds a complete schedule. Concepts explains the underlying model. The API reference lists the public exports.