lib/extensions/string.rb

string.rb

class String
  def to_date_from_br_format
    unless self =~ /(\d{2})\/(\d{2})\/(\d{4})/
      raise "String is not formatted as a brazilian date (#{self})"
    end
    "#{$3}-#{$2}-#{$1}".to_date
  end

  def to_datetime_from_br_format
    unless self =~ /(\d{2})\/(\d{2})\/(\d{4}) (\d{2}):(\d{2})/
      raise "String is not formatted as a brazilian datetime (#{self})"
    end
    "#{$3}-#{$2}-#{$1} #{$4}:#{$5}".to_datetime
  end
end

config/initializers/lib_requires.rb:

require 'extensions/string'