protectedvoid Page_Load(object sender, EventArgs e)
{
    string strCurrDate = "Current date and time: " + DateTime.Now;
    DateTime dtYourDate = DateTime.Parse("09/01/2009 3:39:45 PM"); 
    string strYourDate = "Your date and time: " + dtYourDate.ToShortDateString() + " " + dtYourDate.ToLongTimeString();
    string strTotalHrsElapsed = TotalHoursElapsed(dtYourDate).ToString() + " Hours Elapsed";
    Response.Write(strCurrDate + "<br>" + strYourDate + "<br>" + strTotalHrsElapsed);
}

privatelong TotalHoursElapsed(DateTime dtYourDate)
{
    long lTotalHoursElapsed = 0;

    //Find Current Date and Time
    DateTime dtCurrent = DateTime.Now;

    //Find Time Difference details between current date and your given date
    TimeSpan tsDiff = dtCurrent.Subtract(dtYourDate);

    //Add Total Hours for Days difference
    lTotalHoursElapsed = lTotalHoursElapsed + tsDiff.Days * (24 * 60);

    //Add Total Hours
    lTotalHoursElapsed = lTotalHoursElapsed + tsDiff.Hours;
    
    return lTotalHoursElapsed;
}