convert utc time to 24 hours format (HH:MM:SS) in c#

In addition to Solution 1:

Please see all related methods:
http://msdn.microsoft.com/en-us/library/system.datetime.tostring%28v=vs.110%29.aspx[^].

What you need is formatting. is not "conversion". Note that parameters allows you to format depending on culture (System.Globalization.CultureInfo implements IFormatProvider; http://msdn.microsoft.com/en-us/library/system.globalization.cultureinfo%28v=vs.110%29.aspx[^]) or format string:
http://msdn.microsoft.com/en-us/library/az4se3k1(v=vs.110).aspx[^],
http://msdn.microsoft.com/en-us/library/8kb3ddd4(v=vs.110).aspx[^],
see also http://msdn.microsoft.com/en-us/library/zdtaw1bw%28v=vs.110%29.aspx[^].

—SA