title: Calculate date based on period in php/joomla
body: <p>Anyone knows how to calculate date based on number of week/Month/Year?</p>
  
  <p>suppose if i set the period as 2 weeks, I should get the date 2 week after the current date. If the period is 3 weeks, then, I should get 3 week after current date. Similarly for month and year as well. Can anybody please help with reference code? I am not able to implement this. 
  Is there any predefined function for this?</p>