FA-77172 / Calendar recurrence rules / Member archive

Monthly BYDAY restricted by BYMONTHDAY (Friday the 13th): combine · case 02

BYDAY=FR;BYMONTHDAY=13 returns every Friday and every 13th.

Member previewVariant 2 · 3 implementations · 7 checks per implementation

Case contract

FREQ=MONTHLY with BYDAY weekday codes (MO..SU) and BYMONTHDAY values (negative counts from month end). When both are present a day must satisfy both; an empty list imposes no restriction. Days are examined from dtstart forward. Return the first count ISO dates (search bounded to 50 years).

Why this case matters

Recurring calendar series are expanded into concrete instances for display, reminders and conflict checks.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
only bymonthday	`["2024-01-10", "2024-01-11", "2024-01-12", "2024-01-13"]`	`["2024-01-15", "2024-02-01", "2024-02-15", "2024-03-01"]`	Failed

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