If you're looking for an alternative to the Android calendar, the free version, as well as the paid-for version are good options to consider.
Your calendar - your way
aCalendar stands out for its ability to sync. The application automatically imports all your data and Google Calendars as well as the birthdays of your Facebook friends. At any time, you can choose which calendars you want to see or even which birthdays don't interest you.
Besides being able to deal with a lot of information, one of the main features of aCalendar is that you can choose what you want to see. Each of the views: day, week and month is customizable. From the hours of the day, to showing week numbers or marking Sundays in red (or not), aCalendar is very flexible.
Reminders, meanwhile, can also be programmed to suit you. Among the options, for example, is the ability to assign unusual repetition patterns (e.g. repeating every month and a half).
Moving from the month view to the day view or switching between weeks is actually a pleasure with aCalendar. The application works solely by touch and all the main actions work with movements of your fingers or by holding your finger down on the screen. We recommend watching the brief tutorial to make the most of this app's potential.
In addition, it includes widgets, the design is nice and there are several themes to choose from. You can also assign different colors to calendars and events, which is really convenient for seeing the information clearly. As an added detail, you can even see pictures of your friends on their birthdays.
Among the best of its kind
There are many calendar applications for Android. aCalendar and aCalendar+ are the most comprehensive and intuitive that we've tested. They are definitely excellent alternatives to the original Android calendar.