It’s really very simple to enable the system clock to show military time in Windows 7 or Vista, but the setting is not in an obvious place, so you might not have found it.
To change this setting, we’ll need to get to the Regional and Language Options screen. The easiest way to do so is just enter intl.cpl into the Start menu search box and hit enter. Otherwise, type region into the Control Panel.
From the Regional and Language Options dialog, click the “Customize this format” button, and then select the Time tab.
Change the time format dropdown as shown:
You’ll notice from the key that the capital letter H means 24 hour time, and a single letter means that it won’t display the leading zero.
Windows 7 Military Time
It’s even easier in Windows 7 – just change the drop-down as shown: