title: Calculate length of time between two times in AM/PM
body: <p>I have three <code>DrowDownLists</code>  for selecting start time and another three for selecting end time. I need an asp.net program which will give duration between two time and after i entered start time then end time should be greater than start time. First <code>DrowDownList</code> contains 1 to 12 hours and second contains 0 to 59 minutes and third one is for selecting <code>am/pm</code>.</p>
  
  <p><a href="https://i.stack.imgur.com/E8niL.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/E8niL.jpg" alt="enter image description here"></a></p>
  
  <p>I don't know where to start in codebehind.</p>