Rails 3.2.8 - How do I get the week number from Rails?

Question

I would like to know how to get the current week number from Rails and how do I manipulate it:

1. Translate the week number into date.
2. Make an interval

Answer 1

Date#cweek seems to get the ISO-8601 week number (a Monday-based week) like %V in strftime (mentioned by @Robban in a comment).

For example, the Monday and the Sunday of the week I'm writing this:

[ Date.new(2015, 7, 13), Date.new(2015, 7, 19) ].map { |date|
  date.strftime("U: %U - W: %W - V: %V - cweek: #{date.cweek}")
}

# => ["U: 28 - W: 28 - V: 29 - cweek: 29", "U: 29 - W: 28 - V: 29 - cweek: 29"]