From: Serg Koren <skoren@...>
Date: 2008-02-29T23:48:44+09:00
Subject: Re: Getting number of days in a month -- getting the number of weeks in a year.

That's why i like this group. You learn a lot and get some good Ruby  
code.

On Feb 29, 2008, at 9:32 AM, Rick DeNatale wrote:

> On 2/29/08, Siep Korteling <s.korteling@gmail.com> wrote:
>> Rick Denatale wrote:
>>> On 2/28/08, Serg Koren <skoren@comcast.net> wrote:
>>
>>> (...)
>>
>>> a normal year starting on weekday 1 starts with 52 full weeks and  
>>> ends
>>> with a 'week' of 1 days a total of 53 'weeks.'
>>> a leap year starting on weekday 1 starts with 52 full weeks and ends
>>> with a 'week' of 2 days a total of 53 'weeks.'
>>>
>>
>> (...)
>>
>> Following this analysis:
>>
>> require 'date'
>>
>> def numweeks(year)
>>  start_year = Date.civil(year,1,1)
>>  end_year = Date.civil(year,-1,-1)
>>  (start_year.strftime("%U") .. end_year.strftime("%U")).to_a.size
>> end
>>
>> puts numweeks(2028)   # =>54
>>
>
> Well, that doesn't exactly follow my analysis, but it does work, but
> only if you define the week to start on Sunday.
>
> Another way which DOES follow my analysis
>
> def leap?(year)
>     year % 400 == 0 || year % 4 == 0 && year % 100 != 0
> end
>
> def numweeks(year, start_wday = 0)
>      leap?(year) && Date.civil(year,1,2).wday == start_wday ? 54 : 53
> end
>
> As it turns out, rather unsurprisingly given the world in which we
> live,  numbering the weeks in a year is more complicated than counting
> them.
>
> http://en.wikipedia.org/wiki/Week#Week_number
> http://en.wikipedia.org/wiki/ISO_week_date
> -- 
> Rick DeNatale
>
> My blog on Ruby
> http://talklikeaduck.denhaven2.com/
>