By default, clocks show city names and time zone abbreviations but you can also customize their text. For example, you may want to abbreviate "Los Angeles, CA" to "L.A." or would find it nice to display "Pete" instead of "Bandar Seri Begawan" if Bandar Seri Begawan, Brunei is where you son Peter currently lives.
Choose View > Clocks.
Double-click the clock in the list or select it and choose Edit Clock from the Action pop-up menu (looks like a gear) at the bottom of the list.
Type a text in the "Alternate text" field and click OK.
To switch back to your clock's city name or time zone abbreviation, clear the "Alternate text" field.