GNOME Time Tracker is a combination stop-watch, diary, to-do list tracker and consultant billing system. You can measure the amount of time you spend on a task, associate a memo with it, set a billing rate, print an invoice, as well as track that status of other projects. You do not need to learn or use every feature in GNOME Time Tracker to be productive: it is meant to be quite usable without requiring a deep study of the documentation. But once you have learned to use GNOME Time Tracker effectively, it can be as effective as any desktop organizer.

Features include:

Basic Stop-Watch Support At its core, GTT is a fancy stop-watch: you can click on an icon to start and stop one of any number of timers. It is the times measured by these clocks that make up the core data that GTT works with.
Project Planning Support Well, OK, "project planning" may be an overstatment. But GTT does provide basic to-do list support, including the ability to rank by importance and urgency, specify expected start/stop times, state the project status, and estimate the amount of time needed to complete the project.
Basic Billing/Invoicing Support Infrastructure for storing price & billing information has been put into place. This allows billing invoices to be generated. Tasks can be marked as billable, non-billable, on-hold, or free-of-charge. Billing rates for regular, overtime, double-overtime or flat-fee can be set per task. (Fancier-looking invoices still needed).
Sub-Project Support New projects can be listed as sub-projects of other projects. The time totals will show the total including sub-projects. The Hierarchical tree can be expanded / collapsed to simplify viewing. The tree can be re-arranged by dragging-n-dropping projects.
Simpler Navigation Arrow keys and carriage return now work in the main window. Up/down keys can be used to move up & down. The left/right arrow keys expand/collapse a sub-project list. Hitting return selects the project.
Log Journal A journal showing explicit start and stop times is maintained. Blocks of time can be annotated with memos. The journal can be exported as an html page, or printed (OK, printer support not yet finished).
Auto-merge/cleanup of Short Intervals Support Extremely short intervals (the length is configurable) are automatically removed from the logs. Slightly longer but still short intervals are auto-merged into nearby neighbors. Short gaps between intervals are coalesced as well. You can specify a time period of 0 seconds to turn these features off.
HTML-based GUI The journal GUI is based on extended html pages. If you know HTML, then you can create customized report pages. Particularly handy for slapping the company logo and mailing address on the top of the page, and generating a unique, custom look. User-defined reports (contained in ghtml files) can be added to the menus by typing in the filename into the 'new report' GUI dialog. Typically, a 'user-defined report' is one with customized layout, maybe a logo added, all-spiffed up & such.
Inactivity Timeout An inactivity timeout has been implemented. If the keyboard or mouse have been idle for more than some period of time, then the clock is stopped.
Shell Commands A shell command can be executed whenever a project timer is started or stopped.
Scheme Extension Language Scheme (guile) is used as an extension language, although scheme support is currently limited to report generation.
XML File Format All project and journal data are stored in an XML file format. This should simplify future interoperability and data access concerns.
Multi-Language Support The basic GTT menus have been translated to dozens of languages. Translations are need for the manual. (Actually, the manual needs a re-write).

GNOME Time Tracker is included in the package gnome-utils, which is a part of the GNOME desktop environment. This document describes version 1.4 of GNOME Time Tracker

GNOME Time Tracker can be started by selecting Time Tracking Tool from the Applications submenu of the Main Menu, or by running the command gtt on the commandline.