World Clock Deluxe lets you hide clocks when you don't need them. In addition to that, by hiding clocks you can display different clocks in the palette, in the Dock, and in the menu bar.
Choose View > Clocks.
To show or hide a clock in the Clocks palette, add or remove its checkmark in the Palette column.
To show or hide a clock in the Dock, add or remove its checkmark in the Dock column.
To show or hide a clock in the menu bar, add or remove its checkmark in the Menu Bar column.
You can also use keyboard and mouse shortcuts to quickly show and hide multiple clocks.
Choose View > Clocks.
To show all the clocks or hide the other clocks in the Clocks palette, Option-click a checkbox in the Palette column. You can't hide all the clocks in the palette. At least one clock must always be visible.
To show or hide all the clocks in the Dock, Option-click a checkbox in the Dock column.
To show or hide all the clocks in the menu bar, Option-click a checkbox in the Menu Bar column.
To show or hide a clock simultaneously in the Clocks palette, in the Dock, and in the menu bar, Control-click its checkbox in the Palette, Dock, or Menu Bar column.