If you’d like to display a clean Windows 7 taskbar, you will have to hide the notification area and the system clock which appears on the right side if the Windows taskbar.

To hide the notification area or the system tray which appears in the right side of your Windows taskbar, type gpedit.msc in start search box and hit Enter to open the Group Policy Editor.

Navigate to User configuration > Administrative Templates > Start Menu and Taskbar.

Now double click on the entry Hide the notification area’ Select Enabled button, click Apply > OK.

To hide the System Clock, double click on the entry Remove clock from the system notification area. Select Enabled button, click Apply > OK.

To revert back to the default settings, you have to set it as Disabled or Not Configured.

You can also easily hide the system clock by the following method:
Right click System Clock > Customize notification icons > Turn system icons on/off.

Thats it!