recurring-dates

This is an updated and renamed version of the the-recurring-dates package.

Tiny toolkit for recurring schedules. Exported APIs:

• generateRecurringDates(config): returns { text, dates }
• getRecurringDates(config): shorthand alias
• useRecurringDates(config): React hook that keeps the list in sync

Supports daily, weekly, monthly, and yearly rules with ordinals, weekday filters, custom intervals, and explicit exclusions.

Install

npm install recurring-dates

ESM is the default export. UMD bundles live at dist/index.umd.js for CDN or legacy builds.

Quick Start

import { generateRecurringDates } from "recurring-dates";

const { text, dates } = generateRecurringDates({
  STARTS_ON: "01-01-2025",
  ENDS_ON: "31-01-2025",
  FREQUENCY: "W",
  WEEK_DAYS: ["MON", "THU"],
  EXCLUDE_DATES: ["13-01-2025"],
});

console.log(text); // Every week on MON, THU
console.log(dates); // ["02-01-2025", ...]

import { useRecurringDates } from "recurring-dates";

export function Demo() {
  const dates = useRecurringDates({
    STARTS_ON: "2025-06-01",
    ENDS_ON: "2025-08-31",
    FREQUENCY: "M",
    MONTH_DATES: [1, 15],
    FORMAT: "YYYY-MM-DD",
  });

  return <pre>{JSON.stringify(dates, null, 2)}</pre>;
}

CDN:

<script src="https://cdn.jsdelivr.net/recurring-dates/dist/index.umd.js"></script>
<script>
  const { getRecurringDates } = RecurringDates;
  console.log(
    getRecurringDates({ STARTS_ON: "01-01-2025", ENDS_ON: "05-01-2025" }),
  );
</script>

Config Reference

Key	Type	Notes
STARTS_ON	string	Required. Parsed with FORMAT.
ENDS_ON	string	Required. Must be >= STARTS_ON.
FREQUENCY	"D" "W" "M" "Y"	Defaults to daily.
INTERVAL	number	Defaults to 1. Skips cycles when > 1.
MONTH_DATES	number[]	Days of month for monthly/yearly patterns.
WEEK_DAYS	string[]	ISO weekday codes (MON to SUN).
WEEK_ORDINALS	string[]	FIRST, SECOND, THIRD, FOURTH, FIFTH, LAST (yearly only).
MONTH_NAMES	string[]	JAN to DEC (yearly only).
EXCLUDE_DATES	string[]	Dates to drop after generation.
FORMAT	string	Input/output date format. Default DD-MM-YYYY.
TIMEZONE	string	Optional. IANA timezone identifier (e.g., America/New_York, Europe/London, Asia/Tokyo). Defaults to user's local timezone.

Validation errors return { dates: [], error }. Successful calls omit the error field.

Timezone Support

Use the TIMEZONE option to generate dates in specific timezones. Supports all IANA timezone identifiers.

import { generateRecurringDates, getTimezoneList } from "recurring-dates";

// Generate recurring dates in a specific timezone
const { dates, text } = generateRecurringDates({
  STARTS_ON: "01-01-2025",
  ENDS_ON: "31-01-2025",
  FREQUENCY: "D",
  TIMEZONE: "America/New_York",
});

console.log(text); // Every day
console.log(dates); // ["01-01-2025", "02-01-2025", ...]

// Get list of supported timezones with offsets
const timezones = getTimezoneList();
// [
//   { timezone: "America/New_York", offset: "-05:00", offset_hours: -5 },
//   { timezone: "Europe/London", offset: "+00:00", offset_hours: 0 },
//   { timezone: "Asia/Tokyo", offset: "+09:00", offset_hours: 9 },
//   ...
// ]

// Common timezones
const COMMON_ZONES = [
  "America/New_York", // Eastern Time
  "America/Chicago", // Central Time
  "America/Denver", // Mountain Time
  "America/Los_Angeles", // Pacific Time
  "Europe/London", // UK
  "Europe/Paris", // Central Europe
  "Asia/Tokyo", // Japan
  "Asia/Shanghai", // China
  "Australia/Sydney", // Australia
  "UTC", // Coordinated Universal Time
];

Timezone utilities are exported for advanced usage:

import {
  isValidTimezone,
  getUserTimezone,
  getTimezoneOffset,
  getTimezoneOffsetString,
  formatDateInTimezone,
  getTimezoneList,
  SUPPORTED_TIMEZONES,
} from "recurring-dates";

// Check if a timezone is valid
isValidTimezone("America/New_York"); // true
isValidTimezone("Invalid/Zone"); // false

// Get user's current timezone
const userTz = getUserTimezone(); // "America/New_York"

// Get timezone offset in hours
getTimezoneOffset("Asia/Tokyo"); // 9
getTimezoneOffset("America/New_York"); // -5 (EST) or -4 (EDT)

// Get offset string
getTimezoneOffsetString("Asia/Tokyo"); // "+09:00"
getTimezoneOffsetString("America/New_York"); // "-05:00"

// Format date in specific timezone
const date = new Date(2025, 2, 5);
formatDateInTimezone(date, "America/New_York"); // "03/05/2025"

// Get all supported timezones
const allTimezones = SUPPORTED_TIMEZONES; // Array of IANA timezone strings

Testing

This package includes comprehensive test coverage with 154 passing test cases across 8 test suites:

• daily.test.js - Daily recurrence patterns
• weekly.test.js - Weekly recurrence with weekday filters
• monthly.test.js - Monthly recurrence patterns
• yearly.test.js - Yearly recurrence with ordinals
• current-format.test.js - Date format handling
• edge-cases.test.js - Edge case scenarios
• validation.test.js - Input validation
• timezone.test.js - Timezone support and multi-timezone scheduling (24 timezone tests)

Run tests locally:

npm test              # Run all tests
npm run test:watch   # Watch mode
npm run test:coverage # Generate coverage report

Real-World Use Cases

See TIMEZONE_USECASES.md for 10+ practical examples:

• 🌍 Global team meeting scheduler
• 🏥 Medical appointment reminders across regions
• 🎤 International conference scheduling
• 🔧 SaaS maintenance windows per timezone
• 🔥 E-commerce flash sales by region
• 📅 Project deadline tracking
• 📹 Video release scheduling
• 💪 Gym class schedules across locations
• 💳 Subscription billing by timezone
• 📦 Shipment scheduling for global delivery

Links

• Demo: https://recurring-dates.thehardik.in
• Docs and issues: https://github.com/hardik-143/recurring-dates
• npm: https://www.npmjs.com/package/recurring-dates