By default, a user can delete the logged time at any time. However, if you set the rule about a user deleting his logged time, you can define such rule. 

Here are the steps of how to set the rule for deleting time by your users. 

1. Go to Manage tab and go to Manage Projects page (Figure 1).

 Figure 1 

2. Select a specific project and click Edit button on Manage Projects page (Figure 2). 

 Figure 2 

3. Select Users in the left navigation to show the user list in the project (Figure 3).

 Figure 3 

4. Select the user you want to set rule and click User Settings in Project associated with this user (Figure 4). 

 Figure 4 

5. You will see the page that shows the user's settings in the project. Find Policy for Deleting Logged Time option (Figure 5). 

 Figure 5 

The default value for the rule for deleting logged time is The user can always delete his logged time. You can select a new rule in the drop down list. Once you make the change, you can click Save Changes button to save the changes to make it take affect.