RE: [boost] Re: Boost version 1.30.0 released - date_time change history

From: Jeff Garland (jeff_at_[hidden])
Date: 2003-03-24 07:37:59

> I read on the date_time change history about a new function for
> calculating ISO 8601 week number.
> 
> I should note that this week number is rather useless without
> the corresponding year number. ISO 8601 week-based year is not
> always the same as the actual year. For example, 2nd January 1999
> is week 53 of year 1998 (not 1999!). 30th December 1997 is week
> 01 of year 1998 (not 1997!). (examples taken from the C99 standard)
> 
> My experience is that people often forget about this important fact
> and thus introduce bugs that may be not be catched until such situation
> really happens in life. To force library users consider this thing,
> I think that gregorian::date::week_number should return a pair: week
> number and week-based year number.
>
> Another option would be to just add a separate function for calculating
> week-based year number, however in my opinion it is less desirable
> because of reasons mentined above. In any case, providing week number
> without providing week-based year number is undesirable.

You make a good point that this can be quite confusing.  My thought
would be to add an iso_year() function and some documentation instead 
of changing the current function.

Jeff