Choosing an paying a shareware fee for a clock replacement for Apple's date & time preference is in my opinion getting similar to accepting an invitation to dance in a mine field. Most are overpriced for what they do and many are unstable or lack the one feature you most desire when they meet the other criteria you want.
Soon after you pay the shareware fee many seem to disappear after an update or two or be sold off to someone else who then wants to stick you for another fee. Freeware versions seem to transform into expensive shareware versions after they promise not to. Finally when you finally find a usable basic simple product that does what you want it to do and pay your fee, the developer almost always feels that they have to come out with an "enhanced" version that complicates what was a nice simple and useful product with extra "features" that only a small minority might want or use.
The bottom line: if you don't care for the current selection of available clock replacements, be patient and wait a month instead of spending your money. For in a month you may very well be present with a number of new options and the one sort of would accepted may have disappeared along with some of the ones that you did not like at all.
So do your research, keep informed, try to stay with the freeware products if they can fulfill your needs to avoid the disappointment of spending money for something that you may not be pleased with later on, and enjoy you dance in the mine field of clock replacements.
This product looks like a reasonable candidate for the informed user.