TimeIT is a time tracker that allows users under Ubuntu to track (measure) time they spend on multiple projects and tasks. Having a simple GUI, TimeIT will allow you to measure time you spend on your computer to see which programs and websites that most consume your time by taking into account inactive periods (idle detection).
Install first these dependencies:
sudo apt-get install libgtkmm-2.4-1c2a libxss1
Then install TimeIT with these commands:
wget -O timeit_1.0.0_i386.deb http://goo.gl/EZvCl
sudo dpkg -i timeit_1.0.0_i386.deb