An RRULE (Recurrence Rule) is a string defined by RFC 5545 (iCalendar) that describes a repeating schedule. It's used by Google Calendar, Outlook, Apple Calendar, and most calendar libraries to represent events like 'every Monday at 9 AM' or 'the last Friday of each month'. Example: RRULE:FREQ=WEEKLY;BYDAY=MO,WE;COUNT=10

What does FREQ, INTERVAL, BYDAY, COUNT, and UNTIL mean?

FREQ sets the recurrence type (DAILY, WEEKLY, MONTHLY, YEARLY). INTERVAL is how many units between recurrences (default 1). BYDAY lists days of the week (MO, TU, WE, TH, FR, SA, SU). COUNT limits total occurrences. UNTIL sets an end date in YYYYMMDDTHHMMSSZ format. You can combine these: RRULE:FREQ=WEEKLY;INTERVAL=2;BYDAY=MO,FR;COUNT=20

How do I use an RRULE string in code?

In JavaScript/TypeScript, use the 'rrule' npm package: const rule = RRule.fromString('RRULE:FREQ=DAILY;COUNT=10'). In Python, use the 'python-dateutil' library: rrulestr('RRULE:FREQ=DAILY;COUNT=10', dtstart=datetime.now()). In PHP, use 'simshaun/recurr'. The RRULE string generated here is compatible with all these libraries and with Google Calendar API, CalDAV, and RFC 5545-compliant servers.

What is the difference between COUNT and UNTIL?

COUNT limits the rule to a specific number of total occurrences (e.g. COUNT=10 means exactly 10 events). UNTIL sets an absolute end date — the rule generates events up to and including that date. You can only use one of them at a time; using both in the same RRULE is invalid per RFC 5545.

Does this tool run in the browser or send data to a server?

Everything runs 100% client-side in your browser. No RRULE data, dates, or inputs are ever sent to any server. You can use this tool safely with internal scheduling data or sensitive calendar configurations.

RFC 5545 iCalendar Recurrence Rules

Build Recurring Events
Without Guessing RRULE Syntax

Set frequency, interval, days, and end conditions visually — get a copy-ready RRULE string plus a plain-English summary and a preview of upcoming dates.

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Visual Rule Builder

Pick frequency, interval, days of the week, and end conditions — the RRULE string updates live as you type.

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Parse & Decode

Paste any RRULE string and instantly see its meaning in plain English plus a field-by-field breakdown.

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Occurrence Preview

See the next 10 matching dates so you can verify the rule behaves exactly as expected before shipping.

RRULE Generator

Build or decode RFC 5545 iCalendar recurrence rules — 100% client-side, nothing sent to any server.

Frequency

Interval — every 1 weekly

11530

Days of the week

Start date

End condition

RRULE String

RRULE:FREQ=WEEKLY;BYDAY=MO

Summary

Every week on Monday

Next occurrences

10 shown

1Mon, Jun 15, 2026
2Mon, Jun 22, 2026
3Mon, Jun 29, 2026
4Mon, Jul 6, 2026
5Mon, Jul 13, 2026
6Mon, Jul 20, 2026
7Mon, Jul 27, 2026
8Mon, Aug 3, 2026
9Mon, Aug 10, 2026
10Mon, Aug 17, 2026

Frequently Asked Questions

Everything you need to know about RRULE Generator.

Build Recurring EventsWithout Guessing RRULE Syntax