Here are the steps to add an additional clock to Windows 10.
Step 1: Go to Settings option in Windows 10.
Step 2: Under Settings, click Time & language as in the following screenshot:
Step 3: Go to "Date and time" option.
Step 4: You can see the option of "Add clocks for different time zones." Click it and you can see the "Data and time" options taken. You can add an additional clock with the existing clocks.
Step 5: Now there is another option to add the date, time, and regional settings.
Clicking it you can change the following:
1. Time and data
2. Language
3. Region
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