InputTestHub

RRULE Builder

Builds an iCalendar RRULE from plain choices, explains it in English, and lists the next dates it actually lands on.

Generators Nothing uploaded No sign-up Free, unlimited
Generators tool
2 means every other week, month and so on.
Fill in the fields and press Generate.
In short RRULE Builder is a free online tool on inputtesthub.com that builds an iCalendar RRULE from plain choices, explains it in English, and lists the next dates it actually lands on. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.

How to use the RRULE Builder

  1. Choose the first occurrence — the rule is meaningless without it.
  2. Pick the frequency and the days.
  3. Set an end, or leave it repeating forever.
  4. Check the preview dates before using the rule.

About the RRULE Builder

The RRULE Builder builds an iCalendar RRULE from plain choices, explains it in English, and lists the next dates it actually lands on. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Writing the repeat rule for a generated calendar feed.
  • Checking what "last Friday of the month" actually lands on.
  • Understanding an RRULE someone else wrote.

Details

StandardRFC 5545 section 3.3.10
COUNT and UNTILMutually exclusive — a rule may carry one, never both
UNTILMust be UTC when DTSTART is UTC
Last FridayFREQ=MONTHLY;BYDAY=FR;BYSETPOS=-1
PreviewThe next dates are expanded and listed, not just described
The preview list is the part worth trusting more than the English sentence. Recurrence rules are easy to describe and hard to predict — an interval combined with a monthly nth-weekday rule surprises most people the first time — and seeing twelve real dates settles it.

Where this tool stops

Builds and previews the common rules. RRULE can also express BYWEEKNO, BYYEARDAY, BYHOUR, WKST and negative BYMONTHDAY; those are valid and are not offered here, and the preview would not expand them if pasted in.

Frequently asked questions

Why does the rule need a start date?
Because an RRULE describes only <i>how</i> to repeat, never <i>what</i>. Everything the rule leaves unsaid comes from DTSTART: a weekly rule with no BYDAY repeats on whatever weekday DTSTART falls on, and a yearly rule takes its month and day from it. Pasting an RRULE without its DTSTART into a different event produces a different schedule, and that is the commonest recurrence bug there is.
Can I use both COUNT and UNTIL?
No. RFC 5545 makes them mutually exclusive, and a rule carrying both is invalid — worse, clients disagree about which one to honour, so the series ends at different points for different people. Pick one.
How do I express "the last Friday of every month"?
<code>FREQ=MONTHLY;BYDAY=FR;BYSETPOS=-1</code>. The BYDAY collects every Friday in the month and BYSETPOS picks from that list, with −1 meaning the last. It is not the same as BYDAY=-1FR, which some clients accept and others do not; the BYSETPOS form is the portable one.
What happens on the 31st of a short month?
Nothing — the occurrence is skipped, not moved. A rule set to day 31 fires seven times a year, and the preview above shows exactly which months. If you meant the last day of every month, use BYMONTHDAY=-1, which this builder does not currently offer.
Is the RRULE Builder free, or is there a paid tier?
Free, unlimited, and no email address required. You can use it a hundred times a day and nothing changes.
Is my data uploaded anywhere?
No. The RRULE Builder runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
What problem does the RRULE Builder solve?
The jobs it is built for: writing the repeat rule for a generated calendar feed. Checking what "last Friday of the month" actually lands on. Understanding an RRULE someone else wrote. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Is there anything the RRULE Builder cannot do?
Builds and previews the common rules. RRULE can also express BYWEEKNO, BYYEARDAY, BYHOUR, WKST and negative BYMONTHDAY; those are valid and are not offered here, and the preview would not expand them if pasted in. Knowing where a tool stops being trustworthy matters more than the cases where it works.
What figures does the RRULE Builder work from?
Standard is RFC 5545 section 3.3.10. COUNT and UNTIL is Mutually exclusive — a rule may carry one, never both. UNTIL is Must be UTC when DTSTART is UTC. These are printed on the page itself, so you do not have to take them on trust.
Will this work on a tablet?
Yes. The page is responsive and the page works in Chrome, Safari, Firefox, Edge and Samsung Internet on both Android and iOS. There is no app to install and nothing to sign into.

Related generators tools

All 53
01

QR Code Generator

Creates QR codes for links, WiFi, contacts, email, SMS and plain text, downloadable as PNG or…

02

Barcode Generator

Generates Code 128, EAN-13, UPC-A, Code 39 and ITF barcodes as PNG or SVG with human-readable…

03

Lorem Ipsum Generator

Generates classic Lorem Ipsum placeholder text by paragraph, sentence, word or list item, with…

04

SKU Generator

Builds structured SKU codes from product attributes, with a consistent pattern across a whole…

05

Invoice Number Generator

Generates sequential invoice numbers in your chosen format, with year, month and prefix…

06

WiFi QR Code Generator

Creates a QR code that connects a phone to your WiFi network automatically, without typing the…

08

Countdown Timer Generator

Creates an embeddable HTML countdown timer to any date, in several styles, with no external…

10

vCard (.vcf) Generator

Builds a downloadable .vcf contact file from a simple form, in vCard 3.0 or 4.0, with correct…