[Gretl-users] Re: Problem isoweek() for week 53

On Thu, 6 Aug 2020, Allin Cottrell wrote: > Please read https://en.wikipedia.org/wiki/ISO_week_date

In case it helps, here are the basics of ISO week numbering: * A week starts on Monday and has 7 days, no exceptions. Each day belongs to exactly one ISO week. * A "week-numbering" year has a whole number of weeks: either 52 or, from time to time, 53 (including a "leap week"). This means that such years have either 364 or 371 days, as opposed to 365 or 366 in ordinary calendar years. * So week-numbering years cannot coincide exactly with ordinary years. This may be confusing at first but it's a necessary consequence of the intended regularization.