Change to Military Time

• To enable the 24-hour (military time) clock in Windows XP, click "Start," then click "Control Panel." Double click "Regional and Language Options." Click the "Customize this format" button.
  
  The "Time format" drop-down menu will display the current format, which by default will be "h:mm:ss tt." To change the system tray clock to military time, change this value to either one that begins with a capital "H." The two choices available are "H:mm:ss" and "HH:mm:ss." The difference between these is that the second option will display a leading zero for single-digit times, e.g. "09:00:00." Click "OK," and the clock will be changed.
  
  This method can be used to change to military time in Windows 2000, XP, Vista, and 7.