FA-305 / Calendar arithmetic / Member archive

A calendar year is paired with a week from the previous ISO year · case 05

Dates near New Year receive a week number from one ISO year and a year label from another.

Member previewVariant 5 · 3 implementations · 7 checks per implementation

Case contract

Return YYYY-Www-d for a valid ISO date using ISO week numbering: Monday is weekday one, and week one is the week containing January fourth. The year field is the ISO week year.

Why this case matters

Weekly partition names and report keys can collide or be assigned to the wrong year when calendar and week-based fields are mixed.

One recorded failure

Sample boundary fixture

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

Boundary fixture	Actual	Expected	Outcome
January belongs to preceding ISO year	`"2023-W52-7"`	`"2022-W52-7"`	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.