Question

I try to get a decimal amount of months for a date range. Example:

ruby-1.9.2-p0 > from = Date.new(2011, 7, 6)
 => Wed, 06 Jul 2011 
ruby-1.9.2-p0 > to = Date.new(2011, 8, 31)
 => Wed, 31 Aug 2011 
ruby-1.9.2-p0 > to - from
 => (56/1) 

So the difference is 56 days. But I want and need the amount of months: 1.83

I have created the following piece of code which returns the correct result but doesn’t feel like the ruby way:

months = Hash.new
(from..to).each do |date|
  unless months.key? date.beginning_of_month
    months[date.beginning_of_month] = 1
  else
    months[date.beginning_of_month] += 1
  end
end

multiplicator = 0.0
months.each do |month, days|
  multiplicator += days.to_f/month.end_of_month.day
end

return multiplicator.floor_to(2)

To be honest: It looks ugly and really inefficient. But I just cannot figure out any easier way.
Can you help me to find a better solution?

For further questions feel free to ask me.

Many thanks in advance!

---

Update/Solution: Solved the problem with the following piece of code:

months = 0.0

months += ((date_to < date_from.end_of_month ? date_to : date_from.end_of_month) - date_from + 1) / Time.days_in_month(date_from.month)
unless date_to.month == date_from.month
  months += (date_to - date_to.beginning_of_month + 1) / Time.days_in_month(date_to.month)
  months += date_to.month - date_from.month - 1
end

return months.floor_to(2)

Answer 1

a better way to do would be summation of

• number of days left in from / number of days in from
• number of days completed in to / number of days in to
• number of months between from and to (from, to excluded)

This way you wont have iterations to do