The xclock client displays an analog or digital clock. The digital clock also displays the day, date, time, and year; the format automatically varies for local language custom based on the value of the LANG environment variable. 
The syntax for the xclock client is:
For a complete list of xclock options, refer to the xclock man page. 
The following example creates a digital clock that updates every 10 seconds. 
   xclock -digital -update 10 &
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The next example creates an analog clock that chimes every 30 minutes, updates every 5 seconds, and has yellow hands (all the other colors are the default ones). 
   xclock -analog -chime -update 5 -hd yellow &
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