What happens. A week's date range is printed as Monday's day, Sunday's day, then Sunday's month and year. A week that starts in one month and ends in the next reads as a range that runs backwards inside a single month: next week, 2026-W44 (Monday 26 October to Sunday 1 November), prints as "26–1 Nov 2026", and 2026-W53 as "28–3 Jan 2027".
How to reproduce. crates/vibescrobble-query/src/swarm.rs:672-685 (span, used for the week JSON's dates, the page and the card's when at swarm.rs:268, 648 and 669), and the zine's dates at crates/vibescrobble-query/src/zine.rs:75-89, both format monday.day(), sunday.day(), month(sunday.month()), sunday.year(). Any week whose Monday and Sunday fall in different months hits this. That is about one week in four, including 2026-W44.
Why it matters. The week cards and zine pages are what gets shared, and about a quarter of them name dates that do not exist as written. This is the date formatting, not the copy.
Fixed on main by https://tangled.org/permadeath.com/vibescrobble.com/pulls/339 (b60fa35b): week ranges name each end's month, and its year where they differ.