title: Set the year in a DateTime object
body: <p>How would I go about changing only the year in a datetime object?</p>
  
  <p>I need to call a number of dates from excel, and if the dates I call are before todays date, set the year to 2099. </p>
  
  <p>e.g. date that is called: 15/11/2010 needs to be set to 15/11/2099</p>
  
  <p>Is this doable? or would it be best to change the whole date? </p>