Recurring Events

Create and manage repeating events with powerful RRULE-based recurrence patterns following the iCalendar specification.

Overview

The recurrence system in ilamy Calendar supports creating repeating events using RRULE (Recurrence Rule) patterns based on the iCalendar RFC 5545 specification. Under the hood, it uses the powerful rrule.js library to generate recurring event instances, ensuring robust and reliable recurrence handling.

RFC 5545 Compliant: The recurrence system uses the industry-standard RRULE format powered by rrule.js, ensuring compatibility with other calendar applications when exporting.

Key Features

Flexible Patterns

  • • Daily, weekly, monthly, yearly recurrence
  • • Custom intervals (every 2 weeks, every 3 months, etc.)
  • • Specific weekdays (Mondays and Fridays)
  • • Month-specific patterns (last Friday of month)
  • • Count-based or date-based endings

Advanced Management

  • • Exception dates (skip specific occurrences)
  • • Modified instances (edit individual occurrences)
  • • Dynamic generation within date ranges
  • • Efficient instance filtering
  • • Override detection and handling

Creating Recurring Events

Basic Recurring Event

Create a recurring event by adding an rrule property to your event object: 

import { RRule } from 'rrule'
import dayjs from 'dayjs'

const weeklyMeeting = {
  id: 'weekly-standup',
  title: 'Weekly Team Standup',
  start: dayjs('2025-08-04T09:00:00'),
  end: dayjs('2025-08-04T10:00:00'),
  description: 'Weekly team sync meeting',
  rrule: {
    freq: RRule.WEEKLY,
    interval: 1,
    byweekday: [RRule.MO], // Every Monday
    dtstart: dayjs('2025-08-04T09:00:00').toDate(),
    until: dayjs('2025-12-31T23:59:59').toDate()
  }
}

Common Recurrence Patterns

Daily Meetings

rrule: {
  freq: RRule.DAILY,
  interval: 1,
  dtstart: new Date('2025-08-04T09:00:00'),
  count: 30 // 30 occurrences
}

Bi-weekly Events

rrule: {
  freq: RRule.WEEKLY,
  interval: 2, // Every 2 weeks
  byweekday: [RRule.FR], // Fridays
  dtstart: new Date('2025-08-04T14:00:00'),
  until: new Date('2026-08-04T14:00:00')
}

Monthly on Specific Weekday 

rrule: {
  freq: RRule.MONTHLY,
  byweekday: [RRule.FR.nth(-1)], // Last Friday of each month
  dtstart: new Date('2025-08-04T15:00:00'),
  count: 12 // 12 months
}

Work Week Days

rrule: {
  freq: RRule.WEEKLY,
  byweekday: [RRule.MO, RRule.TU, RRule.WE, RRule.TH, RRule.FR],
  dtstart: new Date('2025-08-04T09:00:00'),
  until: new Date('2025-12-31T23:59:59')
}

Instance Generation

Automatic Generation

The calendar automatically generates recurring event instances within the current view range using rrule.js internally. This happens transparently when navigating between different calendar views: 

// The calendar automatically generates instances
// when you provide a base recurring event
const events = [
  {
    id: 'weekly-standup',
    title: 'Weekly Team Standup',
    start: dayjs('2025-08-04T09:00:00'),
    end: dayjs('2025-08-04T10:00:00'),
    rrule: {
      freq: RRule.WEEKLY,
      byweekday: [RRule.MO],
      dtstart: dayjs('2025-08-04T09:00:00').toDate(),
      until: dayjs('2025-12-31T23:59:59').toDate()
    }
  }
]

// Pass this to IlamyCalendar and instances 
// will be generated automatically for the current view

Handling Overrides

The system automatically handles modified instances and exception dates:

Modified Instances

When you modify a single occurrence of a recurring event, it creates a new event with a recurrenceId that matches the original occurrence time. 

const modifiedInstance = {
  id: 'weekly-standup-modified',
  title: 'Extended Team Standup',
  start: dayjs('2025-08-11T09:00:00'),
  end: dayjs('2025-08-11T11:00:00'), // Extended duration
  recurrenceId: '2025-08-11T09:00:00.000Z', // Original occurrence time
  uid: 'weekly-standup' // Same UID as base event
}

Exception Dates

Use exdates to skip specific occurrences without creating modified instances. 

const recurringEvent = {
  // ... other properties
  rrule: {
    freq: RRule.WEEKLY,
    byweekday: [RRule.MO],
    dtstart: new Date('2025-08-04T09:00:00')
  },
  exdates: [
    dayjs('2025-08-18T09:00:00').toDate(), // Skip this Monday
    dayjs('2025-08-25T09:00:00').toDate()  // Skip this Monday too
  ]
}

RRULE Properties

The RRULE object supports the following properties based on the iCalendar specification. These properties are processed by rrule.js to generate recurring event instances.

rrule.js Documentation: For comprehensive documentation of all RRULE properties and advanced patterns, refer to the rrule.js documentation .

Property Type Description Example
freq Frequency How often the event repeats RRule.DAILY
interval number Interval between occurrences 2 (every 2 weeks)
byweekday Weekday[] Specific days of the week [RRule.MO, RRule.FR]
bymonthday number[] Specific days of the month [1, 15] (1st and 15th)
bymonth number[] Specific months [1, 7] (Jan and July)
dtstart Date Start date for recurrence new Date('2025-08-04')
until Date End date for recurrence new Date('2025-12-31')
count number Number of occurrences 10 (10 times)

Note: You cannot use both until and count in the same RRULE. Choose one termination method.

Advanced Examples

Complex Recurrence Pattern

First Monday of every quarter:

const quarterlyMeeting = {
  id: 'quarterly-review',
  title: 'Quarterly Business Review',
  start: dayjs('2025-01-06T14:00:00'), // First Monday of 2025
  end: dayjs('2025-01-06T16:00:00'),
  rrule: {
    freq: RRule.MONTHLY,
    interval: 3, // Every 3 months
    byweekday: [RRule.MO.nth(1)], // First Monday
    dtstart: dayjs('2025-01-06T14:00:00').toDate()
  }
}

Event with Exceptions and Modifications 

// Base recurring event
const weeklyStandup = {
  id: 'standup',
  title: 'Team Standup',
  start: dayjs('2025-08-04T09:00:00'),
  end: dayjs('2025-08-04T09:30:00'),
  uid: 'standup-series',
  rrule: {
    freq: RRule.WEEKLY,
    byweekday: [RRule.MO, RRule.WE, RRule.FR],
    dtstart: dayjs('2025-08-04T09:00:00').toDate(),
    until: dayjs('2025-12-31T23:59:59').toDate()
  },
  exdates: [
    // Skip these specific dates
    dayjs('2025-08-15T09:00:00').toDate(), // Summer vacation
    dayjs('2025-11-29T09:00:00').toDate()  // Thanksgiving week
  ]
}

// Modified instance for a different time
const modifiedStandup = {
  id: 'standup-modified-aug-20',
  title: 'Extended Team Standup + Planning',
  start: dayjs('2025-08-20T10:00:00'), // Different time
  end: dayjs('2025-08-20T11:00:00'),   // Longer duration
  recurrenceId: '2025-08-20T09:00:00.000Z', // Original time
  uid: 'standup-series'
}

Working with Multiple Time Zones 

// All times should be in consistent timezone
const globalMeeting = {
  id: 'global-sync',
  title: 'Global Team Sync',
  start: dayjs.utc('2025-08-04T14:00:00'), // 2 PM UTC
  end: dayjs.utc('2025-08-04T15:00:00'),
  rrule: {
    freq: RRule.WEEKLY,
    byweekday: [RRule.MO],
    dtstart: dayjs.utc('2025-08-04T14:00:00').toDate(),
    count: 26 // 6 months
  }
}

Best Practices

Consistent UIDs

Use consistent UIDs across the base event and all modified instances to ensure proper override detection.

Date Handling

Always use consistent timezone handling. Convert to UTC for storage and use local timezone for display.

Performance Optimization

Generate instances only for the current view range. The calendar automatically handles this during navigation.

Exception Handling

Use exception dates for simple cancellations and modified instances for changes to time, duration, or other properties.

Integration with Other Features

iCalendar Export

Recurring events are automatically converted to proper RRULE format when exporting to .ics files, maintaining compatibility with other calendar applications.

Calendar Views

All calendar views (month, week, day) automatically handle recurring events, generating and displaying instances as needed for the current view range.

useIlamyCalendarContextiCalendar Export