如何使用收件人的区域设置在Rails 3中发送电子邮件？

en:
  email:
    welcome_subject: "Welcome to My App!"
    welcome_body: "Dear %{name}, welcome to My App!"

class UserMailer < ActionMailer::Base
  def welcome_email(user)
    @user = user
    mail(to: user.email, subject: I18n.t('email.welcome_subject'))
  end
end

<h1><%= I18n.t('email.welcome_subject') %></h1>
<p><%= I18n.t('email.welcome_body', name: @user.name) %></p>