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Recurring Events (RRULE) Support

Chronos MCP now supports recurring events using the RRULE standard (RFC 5545). This allows you to create events that repeat on a regular schedule.

Quick Start

To create a recurring event, simply add the recurrence_rule parameter when creating an event:

# Daily standup on weekdays
create_event(
    calendar_uid="work-calendar",
    summary="Daily Standup",
    start="2025-07-07T09:00:00",
    end="2025-07-07T09:30:00",
    recurrence_rule="FREQ=DAILY;BYDAY=MO,TU,WE,TH,FR"
)

# Weekly team meeting
create_event(
    calendar_uid="team-calendar",
    summary="Team Meeting",
    start="2025-07-08T14:00:00",
    end="2025-07-08T15:00:00",
    recurrence_rule="FREQ=WEEKLY;BYDAY=TU"
)

Supported RRULE Patterns

Daily Recurrence

  • FREQ=DAILY - Every day
  • FREQ=DAILY;INTERVAL=2 - Every other day
  • FREQ=DAILY;BYDAY=MO,TU,WE,TH,FR - Weekdays only
  • FREQ=DAILY;COUNT=10 - Daily for 10 occurrences
  • FREQ=DAILY;UNTIL=20251231T235959Z - Daily until end of year

Weekly Recurrence

  • FREQ=WEEKLY - Every week
  • FREQ=WEEKLY;INTERVAL=2 - Every other week
  • FREQ=WEEKLY;BYDAY=MO,WE,FR - Every Monday, Wednesday, Friday
  • FREQ=WEEKLY;BYDAY=SA,SU - Weekends only

Monthly Recurrence

  • FREQ=MONTHLY - Same day each month
  • FREQ=MONTHLY;BYMONTHDAY=15 - 15th of each month
  • FREQ=MONTHLY;BYMONTHDAY=-1 - Last day of each month
  • FREQ=MONTHLY;BYDAY=2MO - 2nd Monday of each month
  • FREQ=MONTHLY;BYDAY=-1FR - Last Friday of each month
  • FREQ=MONTHLY;INTERVAL=3 - Quarterly (every 3 months)

Yearly Recurrence

  • FREQ=YEARLY - Anniversary of start date
  • FREQ=YEARLY;BYMONTH=3;BYMONTHDAY=15 - March 15th each year
  • FREQ=YEARLY;BYMONTH=12;BYMONTHDAY=25 - Christmas
  • FREQ=YEARLY;BYDAY=1MO;BYMONTH=9 - Labor Day (1st Monday in September)
  • FREQ=YEARLY;INTERVAL=2 - Every other year

RRULE Components

Required Component

  • FREQ: Frequency of recurrence (DAILY, WEEKLY, MONTHLY, YEARLY)

Optional Components

  • INTERVAL: How often to repeat (default: 1)
  • COUNT: Total number of occurrences
  • UNTIL: End date/time for recurrence (YYYYMMDDTHHMMSSZ format)
  • BYDAY: Days of week (MO, TU, WE, TH, FR, SA, SU)
    • Can include position for monthly: 2MO (2nd Monday), -1FR (last Friday)
  • BYMONTHDAY: Day of month (1-31, or -1 for last day)
  • BYMONTH: Month number (1-12)

Validation Rules

Chronos MCP validates RRULE syntax before creating events:

  1. FREQ is required - Every RRULE must start with FREQ=
  2. Valid FREQ values - Only DAILY, WEEKLY, MONTHLY, YEARLY are supported
  3. Positive integers - INTERVAL and COUNT must be positive integers
  4. Valid day codes - BYDAY must use standard day abbreviations
  5. Date format - UNTIL must be in YYYYMMDD or YYYYMMDDTHHMMSSZ format

Examples

Meeting Room Booking (Every Tuesday and Thursday)

create_event(
    calendar_uid="facilities",
    summary="Conference Room A Reserved",
    start="2025-07-08T13:00:00",
    end="2025-07-08T14:00:00",
    recurrence_rule="FREQ=WEEKLY;BYDAY=TU,TH;UNTIL=20251231T235959Z"
)

Monthly Reports (Last Friday of each month)

create_event(
    calendar_uid="deadlines",
    summary="Monthly Report Due",
    start="2025-07-25T17:00:00",
    end="2025-07-25T17:30:00",
    recurrence_rule="FREQ=MONTHLY;BYDAY=-1FR"
)

Quarterly Reviews (Every 3 months on the 15th)

create_event(
    calendar_uid="management",
    summary="Quarterly Performance Review",
    start="2025-07-15T10:00:00",
    end="2025-07-15T11:00:00",
    recurrence_rule="FREQ=MONTHLY;INTERVAL=3;BYMONTHDAY=15"
)

Error Handling

If an invalid RRULE is provided, Chronos MCP will return an error:

# This will fail - FREQ is required
create_event(..., recurrence_rule="BYDAY=MO")
# Error: Invalid RRULE: RRULE must start with FREQ=

# This will fail - invalid frequency
create_event(..., recurrence_rule="FREQ=HOURLY")
# Error: Invalid RRULE: Invalid FREQ value: HOURLY

# This will fail - invalid day code
create_event(..., recurrence_rule="FREQ=WEEKLY;BYDAY=MONDAY")
# Error: Invalid RRULE: Invalid day abbreviation: MONDAY

Limitations

  • Only supports DAILY, WEEKLY, MONTHLY, and YEARLY frequencies
  • Does not support HOURLY, MINUTELY, or SECONDLY frequencies
  • Complex patterns with multiple BYMONTH or BYSETPOS are not validated
  • Exception dates (EXDATE) are not yet supported
  • Modification of recurring event instances not yet implemented

Future Enhancements

  • Support for modifying individual occurrences
  • Exception dates (EXDATE) for skipping specific occurrences
  • More complex recurrence patterns
  • Timezone-aware UNTIL dates