#php funny quirks. We just stumbled upon a problem in production where we were sharding datas using Year and Week syntax.
The code was something like $Suffix = $now->format("YW"). Well, turns out 2024-12-31 returns 202401 as Suffix because Year is 2024 and week would be 53.
Long story short, format has a macro macro "o" that returns ISO8601 year, so $now->format('oW') returns 202501 correctly for last days of the year.
That's one of those corner case you'd never take in consideration.
@necrophcodr Yep, seems the "An year always have 52 weeks" is just on spot. Frankly speaking I'd expected 202453.