Project Hamster is a Gnome time tracker that is a default application on Debian installs.
Ranked in these QuestionsQuestion Ranking
Pro Provides a good overview of activity
An overview of all tracked activity over a day, a week, or a month is available that helps get an understanding of how activity is distributed over time. The overview can also be exported to an HTML file that's intended for printing.
Pro Multiple ways to categorize activity
All activity entries can be put into categories and have multiple tags assigned to them.
Pro Long-term support guaranteed
As a Gnome application it is supported by a mature community of more than 100 contributors.
Pro Easy to use
One click to access the app.
Con Does not scale for HIDPI displays
The text and buttons in this app do not scale for larger resolution displays making for a difficult to use app when using native 4k resolutions.
Con No activity is tracked automatically
Unlike other apps that automatically are capable of tracking for example which apps are open, Hamster requires add all activity manually.
Con Only compatible with Gnome 3
If you use another desktop environment it will feel out of place as it is specifically developed with Gnome 3 in mind.