Time tracking is not automatic. There are applications that do that very well such as ManicTime. However, in our experience there is limited value because software you are using doesn't really tell you that much about what you are actually working on. For example, you could spend a large portion of your day using Outlook to respond to emails. However, that time might be spent spread across multiple clients or projects. So then you must spend additional time mining the data to find meaning.
Our approach is different. You decide what the various tasks are for a project and then start a timer as you begin working on each task. At the end of a week (or any time period of your choosing) the data is already organized by the client/project/task. This also allows you to account for time spent working while away from your computer. For example, if you are a designer, you may spend a bunch of time working on a whiteboard or a sketch pad. When you get back to your desk, you can add a time entry to account for your time.