ruby – 我怎样才能找到一年前同一周的日期？

这是一周的例子,从星期日到星期六：

11/21/2010 - 11/27/2010

我想找到周日至周六同一周的日期,仅限去年.

解决方法

require 'date' # Included in Ruby's standard library,no gem needed
Now = Date.today
before = Date.civil( Now.year-1,Now.month,Now.day )
sunday = Date.commercial( before.year,before.cweek,1 ) - 1 # Day 1 is Monday
this_week_last_year = sunday..(sunday+6)

编辑：虽然Date.commercial很酷,但不需要.这是一个更简单的方法来查找本周开始的星期日：

require 'date'
Now    = Date.today
before = Date.civil( Now.year-1,Now.day )
sunday = before - before.wday