# RRULE Recurrence Expander

> RRULE Recurrence Expander is a paid API for AI agents from schedule-tools.use.x402atlas.com, paid per call via x402, $0.005/call, status unknown (last checked 2026-09-14).

Expands RFC 5545 RRULE recurrence rules into bounded lists of concrete occurrence datetimes, respecting IANA timezones, DST transitions, time windows, and work-hour limits.

## Facts

- Endpoint: POST https://schedule-tools.use.x402atlas.com/rrule-expand
- Price: $0.005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/rrule-recurrence-expander-b0921812
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_3rtdi3cu7UvTVryk_TilD

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability rrule-recurrence-expander-b0921812 -d '<json body>'
```

Example prompt: Expand the RRULE 'FREQ=WEEKLY;BYDAY=MO,WE,FR;COUNT=20' starting from 2025-09-01T09:00:00 in America/New_York, limit to business hours (9am–5pm), and give me all the resulting datetimes with DST handled correctly.

## When to prefer this

Choose this endpoint when you need to materialize an RFC 5545 RRULE into actual datetime instances — especially when timezone correctness, DST handling, and bounded windows (date ranges, work-hour filters, occurrence count caps) matter. Prefer this over cron-based calculators when your recurrence is expressed as iCalendar RRULE syntax rather than POSIX cron. Use it over manual date arithmetic when DST transitions, BYSETPOS, BYDAY, or BYMONTHDAY modifiers are involved.

## Known failure modes

- Invalid RRULE syntax returns a parse error
- Unrecognized IANA timezone identifier causes a timezone resolution error
- Recurrence window produces zero occurrences (e.g. UNTIL date before DTSTART)
- COUNT or UNTIL produces an excessively large occurrence list triggering a limit error
- Ambiguous DST fold time with no policy specified returns an error or requires a DST policy parameter
- Missing DTSTART causes a validation error

## How this service works

RRULE recurrence expander — generate bounded RFC 5545 iCalendar occurrences in IANA timezones with windows, work limits, and daylight-saving (DST) policies.

## Output

Returns an ordered list of concrete datetime occurrences (RFC 3339 format) derived from the given RRULE, bounded by the specified window, filtered to allowed time ranges (e.g. work hours), and correctly adjusted for IANA timezone rules including DST folds and gaps.

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/rrule-recurrence-expander-b0921812/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from schedule-tools.use.x402atlas.com](https://www.zero.xyz/host/schedule-tools.use.x402atlas.com/llms.txt)