NextishClock 1.0 for Mac is available as a free download on our application library. The actual developer of this free software for Mac is Peter MacWhinnie. The software lies within Theming Tools, more precisely Multiple Desktops.
From the developer:
NextishClock is an alternative to Apple's Window Clock, it has a few extra features such as themes and a calendar.
You may want to check out more software for Mac, such as Cisdem WindowManager for Mac, which might be similar to NextishClock.