FA-59399 / Subscription proration billing / Member archive

Month-end anchored renewal dates: zero-based month index · case 04

Every renewal is scheduled one month late.

Member previewVariant 4 · 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	`[[2023, 7, 28], [2023, 10, 28], [2024, 1, 28], [2024, 4, 28], [2024, 7, 28], [2024, 10, 28], [2025, 1, 28], [2025, 4, 28], [2025, 7, 28], [2025, 10, 28], [2026, 1, 28], [2026, 4, 28], [2026, 7, 28], [2026, 10, 28]]`	`[[2023, 6, 28], [2023, 9, 28], [2023, 12, 28], [2024, 3, 28], [2024, 6, 28], [2024, 9, 28], [2024, 12, 28], [2025, 3, 28], [2025, 6, 28], [2025, 9, 28], [2025, 12, 28], [2026, 3, 28], [2026, 6, 28], [2026, 9, 28]]`	Failed

MEMBER ARCHIVE

The complete case is available to members.

This record includes three runnable implementations, regression fixtures, execution results, and source hashes.

Member access is invitation-based. Sign in with your invited account to inspect the sources.