aCalendar+ Calendar & Tasks, developed by Tapir Apps GmbH, is a paid Android calendar app that costs $4.49 and has zero in app purchases.
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Pro Good Tasks integration
Tasks get shown in the calendar, although there is also a separate tasks view. It supports Google Tasks and recurring tasks.
Pro Lots of customization options
The settings menu is rather detailed and includes a good selection of color themes to choose from, possibility to adjust font-size, set beginning and end of day, ability to choose what views to use and more.
Pro Good fullscreen widgets for all views
The app has widgets for day, week and month views.
Pro Very convenient user interaction
Switching from day<->week<->month views by swiping laterally is a powerful feature.
Pro Nice presentation
The three views are very convenient, particularly the week view, which shows the week position inside the month
Pro Can add public holidays to calendar from over 35 countries
For the 30+ available languages for the app, there are holiday calendars available to be added.
Pro Free, ad-less version available
aCalendar is an Android app that comes in free, ad-less version as well as this paid version.
This paid version aCalendar+ adds more features like agenda view, home screen widget and the ability to manage Google Calendars. The developer also donates some of the profits from this Pro version to help protect the endangered mountain tapir.
Pro Lunar calendar support
aCalendar can be set up to use a calendar based on cycles of the lunar phases.
Pro Color-coding support
The app has 48 calendar and 12 event colors.
Pro Unique Week overview
Its week overview is very well suiting for tasks and all day events. It shows everything at once.
Pro Available in 30 languages
There are 3o user made translations available for the app, making for a good calendar to use in different countries.
Pro QR and NFC barcode sharing of events
Using both QR codes as well as NFC, users can share events wirelessly and easily
Pro Useful 3-finger tap to go to today
By utilizing a three finger tap shortcut users can easily got to the today view from anywhere in the app.
Drag'n'drop functionality is available in day view with this paid version of the application.
Con Free version is very limiting
Free version of the application does not include common things like the agenda view, actionable notifications or attendee management among many other more advanced features.