aCalendar+ is still BETA software - please try the free aCalendar version first!
There are not that many additional features ready yet, but buying aCalendar+ supports development, especially as I can buy some more Android devices for testing.

EXTRA FEATURES (aCalendar+ only)

Month widget
NFC sharing (if supported by the device)
Privacy and availibility settings

Features:

intuitive navigation with smooth transitions
day, week & month calendar
Fullscreen widgets
flexible recurrences
birthdays & anniversaries with photos from your addressbook and editing
uses Android's native calendar backend and synchronization
no battery drain
moon phases and zodiac signs for birthdays
QR barcode sharing of events
12/24h clock honoring system settings
optimized text display and improved line-break

PERMISSIONS
On top of the basic calendar and contact permissions also necessary for the free version, aCalendar+ also asks for Internet and NFC. Internet will be used in the future for Google Tasks and potentially other services. aCalendar+ respects your privacy and will NEVER send any of your private data anywhere unless configured by YOU. 'Send Email to guests' is bound to 'write calendar data' by Google.

TRANSLATIONS
aCalendar+ is translated into over 20 languages - please let me know if there is a bad translation somewhere.

LOVE
♥ If you like aCalendar+, you can show your support by rating 5-stars and recommending it to your friends

ROADMAP (Planned features)

more calendar widgets
agenda view and widget
Google Tasks integration
more calendar import/export options
Color-coded categories (requires Android 4.0.3+)
alternative calendar system support (Bahá'í, Chinese, Ethiopian, Hebrew, Indian, Iranian/Persian, Islamic/Hijri, Thai, Zoroastrian)
send YOUR feature requests to support@tapirapps.de

What's in this version : (Updated : May 5, 2012)

New next 7 days widget
Custom transparency in widget
App starting view is now independent from widget view
Screen rotate in event edit no more resets values
Using phone timezone for new event instead of calendar timezone (was misconfigured for too many people)
Let me know if there are problems! I cannot answer you on comments in the Play Store so please contact me at support@tapirapps.de
Also if you like aCalendar+ I'd appreciate it if you give a good rating and recommend it to your friends.

Required Android O/S : 2.1+
Download : 350Kb APK

Screenshots :

Download here