Passing Javascript value from one page to another in asp.net?

Hi experts,  Sorry to bother you one more time.
I am not sure whether to post this on JavaScript forum or here. Please forgive me if I posted at the wrong forum. I have a javascript that calculates the different between start time and end time. The value of the difference is stored in a variable called hourDiff.
var hourDiff = endDate - startDate;
Below, I am passing some form variables from one page to another page called Reserve.aspx using asp.net. Code is below:
<div class="bbcode_container"> <div class="bbcode_description">
<asp:HyperLink ID="siteId" style="color:#111" runat="server" navigateurl='<%# String.Format("Reserve.aspx?id={0}&groupsize={1}&facilityFees={2}&extrahour={3}&depoitAmt={4}&cancelAmt={5}&keydeptAmt={6}", Eval("siteId"), Eval("capacity"),Eval(&quo ...