get system dateandtime in 24 hour format

var dt = DateTime.Now;
Console.WriteLine(dt.ToString("MM/dd/yyyy HH:mm"));

In addition to Solutions 1 and 2, pay attention for two different methods, where the format depends on particular culture:
http://msdn.microsoft.com/en-us/library/ht77y576.aspx[^],
http://msdn.microsoft.com/en-us/library/8tfzyc64.aspx[^].

Please also see:
http://msdn.microsoft.com/en-us/library/system.globalization.cultureinfo.aspx[^],
http://msdn.microsoft.com/en-us/library/system.iformatprovider.aspx[^].

As System.Globalization.CultureInfo implements System.IFormatProvider, you can use its instance as a parameter (please see the code sample in second link). Some cultures may already provide the format you need.

—SA

HH - hours on 24-hour scale.

Dim datee As String = Format(Now, "MM/dd/yyyy HH:ss")