The incompatibilities with System Preferences' custom date and time formats on macOS 10.4 have been solved.
World Clock Deluxe now supports the 1-24 and 01-24 hour formats.
A bug which could cause version 4.1 to crop clocks on macOS 10.3 when the Gujarati, Hindi or Marathi format was selected in the International pane of System Preferences has been fixed.
Some other minor bugs have been fixed and some other minor improvements have been introduced.