Create Digital Clock On Excel

=TEXT(HOUR(NOW()),"00")&":"&TEXT(MINUTE(NOW()),"00")&":"&TEXT(SECOND(NOW()),"00")

You can create a clock in Excel 2003,2007,2010 in one or any cells using this formula's for Day, Month & Year you can uses the excel NOW function

=NOW( ) 

The Format the cell according to you need

Formatting Process :-

Ctrl+F1 => Number => Date => Select format.