How to Add and Switch Clocks in Windows 8.1
If you want to change the clock in the lower-right corner of the Windows 8.1 desktop — perhaps add a clock, change the time, or change the format of the date or time — it’s easy. Here’s how:
In the lower-right corner of the desktop, tap or click and hold on the clock. Choose Adjust Date and Time.
The Date and Time dialog box appears.
To change the current date and time or set up a new time zone, tap or click the appropriate buttons.
Be aware that some calendar programs don’t take kindly to having their time zones changed. Some of them get confused and can’t decide whether to adjust the time of your appointments or leave them as is. (If you were in Los Angeles when you set an appointment for 9:00 Monday morning and you fly to New York, what should happen to your appointment? It’s not a simple question!)
To change the date format (to show day-month-year, for example), tap or click the Change Date and Time button and then tap or click the Change Calendar Settings link.
(Optional) To put a second digital clock in the system notification area — the bottom-right corner of the desktop — tap or click the Additional Clocks tab and follow the instructions.
When you’re happy with the changes, tap or click OK.
Your clocks change at once.