FA-59400 / Subscription proration billing / Member archive

Month-end anchored renewal dates: zero-based month index · case 05

Every renewal is scheduled one month late.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Input {anchor [y,m,d], n, interval months}. Renewal i (1..n) falls interval*i months after the anchor month, on the anchor day clamped to that month's length (so a 31st anchor returns to the 31st whenever possible). Return the list of [y, m, d].

Why this case matters

Month-end anchors must not drift to the 28th after February, and leap years change the clamp.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
regression 0	`[[2024, 5, 29], [2024, 7, 29], [2024, 9, 29], [2024, 11, 29], [2025, 1, 29], [2025, 3, 29]]`	`[[2024, 4, 29], [2024, 6, 29], [2024, 8, 29], [2024, 10, 29], [2024, 12, 29], [2025, 2, 28]]`	Failed

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