In order to get the most from a time reporting system, several requirements should be met.  Historical data that is accumulated in the system will be more accurate and meaningful depending on the way team members report their hours.

Periodicity is very important.  Time reports are usually more accurate when team members update their hours daily.  If reporting is done weekly, team members will hardly remember how much time they spent on each task at the beginning of the week.

Insist that team members report their hours accurately.  Sometimes people don’t work exactly 8 hours a day, so when time reports are “flat” (i.e. 8 hours every day), you may be looking at a symptom of inaccurate reporting.

It is also important to break down the tasks in meaningful sub-tasks, so team members won’t be confused when reporting their hours.  If possible, include a description of the tasks; this description will serve as a future reference for post-mortem analysis and historical data retrieval.

Finally, it is not recommendable to use reported hours as a criteria to reward team members.  Doing so may introduce more biases in the reports and may cause a negative team response.