days_in_month (ActiveSupport::CoreExtensions::Time::Calculations::ClassMethods)

    # File lib/active_support/core_ext/time/calculations.rb, line 16
              def days_in_month(month, year=nil)
                if month == 2
                  !year.nil? && (year % 4 == 0) && ((year % 100 != 0) || (year % 400 == 0)) ?  29 : 28
                elsif month <= 7
                  month % 2 == 0 ? 30 : 31
                else
                  month % 2 == 0 ? 31 : 30
                end
              end