Jquery time difference in hours from two fields

Question

I have two fields in my form where users select an input time (start_time, end_time) I would like to, on the change of these fields, recalcuate the value for another field.<

Answer 1

   var start = '5:30';
   var end = '7:50';
   s = start.split(':');
   e = end.split(':');
   min = e[1]-s[1];
   hour_carry = 0;
   if(min < 0){
       min += 60;
       hour_carry += 1;
   }
   hour = e[0]-s[0]-hour_carry;
   min = ((min/60)*100).toString()
   diff = hour + ":" + min.substring(0,2);
   alert(diff);