How to Calculate the Total Duration in Hours ?

Question

Hello,<br />&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;I have the Start time and End time using Bootstrap timepicker, I need a result total Duration in Hours and Minutes , How to Calculate the Spending Hours .? yet now i am trying the Start time(10AM) and End time (10 PM) Total Hours is =12Hours ,but i get result is 0 hrs , till now i am calculating the Numbers only . I dont know how to calculate the time Duration for 24 hours ,In the Below i am attached the Source code till Now i tried ,Kindly give the solution&nbsp;<br /><div>My Expected result is Highlighted in the red color:</div><div>&nbsp;</div><div>Source Code <img src="/forums/uploadfile/c21ee8/10052016005528AM/Time Duration.PNG" alt="" />&nbsp;</div><div>&nbsp;</div><div>&nbsp;</div>Thanks &amp; Regards&nbsp;<br />Felish