ASP .NET C# Show Only Hourly DateTime values from an Array of 24 hour values.

Someone tried to answer this question yesterday but that solution did not work. I am reposting it. Looks like no one has a solution to my question (even in other forums outside of EExchange). So here we go again. The output of the response.write can be seen in:
http://www.cameradisplay.com/CondorStats/tempdisplaytime.htm

These are 360 different time values, spanning 24 hours, separated from each other by 4 minutes. How can I just show these values in separated by Hourly spans while the intermediate values simply get replaced by blank space (the chart's X-Axis cannot accomodate all 360 values).

 DateTime startTime = Convert.ToDateTime(dayArray[0]);
                DateTime endTime = Convert.ToDateTime(dayArray[dayArray.Length - 2]);
                TimeSpan timeSpan = (endTime - startTime);
                //Response.Write(startTime.ToString() + " " + endTime.ToString() + " " + timeSpan.ToString());
                for (int i = 0; i < dayArray.Length - 2; i++)//loop to one less because of extra comma/space at end
                {
                    DateTime currentTime = Convert.ToDateTime(dayArray[i]);
                    Response.Write(currentTime.ToString() + "<br>");

                }