BusyCal comes as an alternative to using Mac's Calendar tool for keeping track of your future events, such as business meetings, birthdays, etc. Unlike Mac's utility, BusyCal is capable of syncing stored data with iCloud, Google Calendar, Office 365 and Exchange in just a few moments.
What's more, you can use the tool to schedule events, set various types of alarms for future tasks, import and manage contacts, etc. It also gives you access to accurate weather info.
In the Preferences panel of the utility, you will find a wide range of settings. You can choose between multiple view options, display birthdays and US holidays, select the preferred font style and size, and so much more. It also brings you a panel in your Menu Bar that displays info about the current month, future events, etc. You can hide the tool's panel if needed.
One of the things that bother me is that BusyCal doesn't bring you an integrated help manual. It took me a while to find certain calendar options and import data from my Google account. Furthermore, in my testing, I noticed that some types of calendars don't support to-dos (Google calendar).
Another aspect you need to consider is that you can find cheaper solutions.
So, it's up to you to decide if it's worth buying this Mac Calendar alternative for your computer or not.