How do I add two weeks to Time.now?

How can I add two weeks to the current Time.now in Ruby? I have a small Sinatra project that uses DataMapper and before saving, I have a field populated with the current time PLUS two weeks, but is not working as needed. Any help is greatly appreciated! I get the following error:

NoMethodError at /
undefined method `weeks' for 2:Fixnum

Here is the code for the Model:

class Job
  include DataMapper::Resource

  property :id,           Serial
  property :position,     String
  property :location,     String
  property :email,        String
  property :phone,        String
  property :description,  Text
  property :expires_on,   Date
  property :status,       Boolean
  property :created_on,   DateTime
  property :updated_at,   DateTime

  before :save do
    t = Time.now
    self.expires_on = t + 2.week
    self.status = '0'
  end
end