In Javascript the Date object can also deal with time. To do date or
time arithmetic you need to convertthe input values into a standard time
(valueOf returns the number of milliseconds between midnight Jan1, 1970
and the Date and time set in the object). If all input are set this way
then subtracting the two times that you want would yield you a result in
millioseconds then you can convert that to the appropriate units that
you want.If you are new to Javascript then this might be a bit
much.......