RRULE API

API ID 13510

Expands an iCalendar RRULE into occurrence dates between a start and end time.

15 ms avg response

API Documentation

Endpoints

Request
Expands an iCalendar recurrence rule into occurrence timestamps between a start time and an end time. Send rrule, startTime, and endTime in the JSON body. Invalid rules or timestamps return HTTP 400. The rrule parameter is an RFC 5545 recurrence rule string. Parts are separated by semicolons. FREQ is required. FREQ (required). One of: YEARLY, MONTHLY, WEEKLY, DAILY, HOURLY, MINUTELY, SECONDLY Optional parts: INTERVAL: positive integer (every N periods). Default 1 COUNT: number of occurrences UNTIL: end datetime in iCalendar form, for example 20260814T235959Z WKST: week start. One of MO, TU, WE, TH, FR, SA, SU. Default MO BYDAY: weekdays, comma-separated. MO, TU, WE, TH, FR, SA, SU. Optional nth prefix such as 1MO or -1FR BYMONTH: 1 to 12 BYMONTHDAY: 1 to 31 or negative from end of month BYYEARDAY: 1 to 366 or negative BYWEEKNO: 1 to 53 or negative BYSETPOS: integer positions in the recurrence set BYHOUR: 0 to 23 BYMINUTE: 0 to 59 BYSECOND: 0 to 59 Examples: FREQ=DAILY FREQ=WEEKLY;BYDAY=MO,WE,FR FREQ=MONTHLY;BYMONTHDAY=1 FREQ=YEARLY;BYMONTH=12;BYMONTHDAY=25 FREQ=WEEKLY;INTERVAL=2;BYDAY=TU
Endpoint ID: 29947
POST https://creators.zylalabs.com/api/13510/rrule+api/29947/expand+rrule
INPUT PARAMETERS

Expand RRULE — Endpoint Features

Object Description
Request Body Required Json

Free test requests remaining: 3 of 3.


INPUT PARAMETERS

API EXAMPLE RESPONSE
JSON
{
    "message": "Completed successfully",
    "dateList": [
        "2026-08-03T09:00:00Z",
        "2026-08-05T09:00:00Z",
        "2026-08-07T09:00:00Z",
        "2026-08-10T09:00:00Z",
        "2026-08-12T09:00:00Z",
        "2026-08-14T09:00:00Z"
    ]
}
Expand RRULE — CODE SNIPPETS

curl --location --request POST 'https://zylalabs.com/api/13510/rrule+api/29947/expand+rrule' --header 'Authorization: Bearer YOUR_API_KEY' 

--data-raw '{
  "rrule": "FREQ=WEEKLY;BYDAY=MO,WE,FR",
  "startTime": "2026-08-03T09:00:00Z",
  "endTime": "2026-08-14T23:59:59Z"
}'

    

API Access Key & Authentication

After signing up, every developer is assigned a personal API access key, a unique combination of letters and digits provided to access to our API endpoint. To authenticate with the RRULE API simply include your bearer token in the Authorization header.

Headers
Header Description
Authorization Required Should be Bearer access_key. See "Your API Access Key" above when you are subscribed.

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Overview

Expands an iCalendar RRULE into occurrence dates between a start and end time.

RRULE API FAQs

The RRULE API returns a success message along with a `dateList`, which is an array of RFC 3339 timestamps representing each occurrence of the specified recurrence rule within the given time window.

The key fields in the response data are `message`, which indicates the success of the operation, and `dateList`, which contains the array of occurrence timestamps generated from the provided RRULE.

The Expand RRULE endpoint accepts three parameters: `rrule` (the recurrence rule string), `startTime` (the start timestamp in RFC 3339 format), and `endTime` (the inclusive end timestamp in RFC 3339 format).

The response data is organized in a JSON format, containing a `message` field for status and a `dateList` field that holds an array of timestamps. Each timestamp corresponds to an occurrence of the recurrence rule within the specified time frame.

Typical use cases include calendar and scheduling applications that need to generate specific dates from a stored RRULE, as well as booking systems, reminders, and job schedulers that require expanded date patterns for a defined range.

Users can utilize the returned `dateList` to schedule events, send reminders, or populate calendars with specific occurrence dates. Each timestamp can be directly integrated into scheduling systems or applications that require precise date information.

If the provided RRULE or timestamps are invalid, the API will return an HTTP 400 error, indicating a bad request. Users should ensure that their inputs conform to the expected formats to avoid this error.

Users can customize their data requests by modifying the `rrule`, `startTime`, and `endTime` parameters. By changing these values, users can generate occurrence dates for different recurrence patterns and time frames as needed.

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