Almanah Diary (previously just “Diary”) is a small application to allow you to keep a diary of your life. It has editing abilities, including text formatting and printing. It lists events which happened (on your computer) for each day (such as Evolution tasks and appointments), and allows terms used in diary entries to be “defined” across the set of entries, to allow you to log things which were present over longer periods in more detail.
Install almanah in Ubuntu
sudo apt-get install almanah
Open almanah from Applications--->Accessories--->Almanah Diary
Once it opens you should see similar to the following screen here select date and enter your tasks