iClock is a program designed to help you manage your time more efficiently. With its help, you can monitor the time in various cities from around the world, set reminders for important events, define work break alarms, count time on your Mac, and so much more.
The utility provides you with two separate menus which can be accessed from your status bar. One menu is for keeping track of time while the other one is for displaying calendar information.
You can choose which type of info to be displayed in the time menu. For example, you can configure the program to show you the current time in 3 or 4 cities, display your real IP address, etc. All settings can be found in the Preferences panel -> Time menu and can easily be configured even by beginner Mac user.
As for the built-in calendar tool, you can configure the utility to show the current month and customize its appearance according to your needs. For instance, you can change the color of the background section and choose which type of info to be displayed (national, religious or sports holidays correspondent to your country).
The only disadvantage I found while testing the program was the fact that it offered support for a limited amount of audio formats when setting local files as alarm sounds. Popular formats like OGG or FLAC aren't compatible with the tool. Still, this isn't a big deal as the program delivers what's being promised on the homepage of the developer. So, I'd say it's worth a shot.