Allow time entries with negative durations. It is OK if this is only for time entries without a project, task, ... filled in. Just like 'absence' entries. This way, if a resource has 10 hours of time entries for a day, while they should only work 8 hours, we can generate (or create) a time entry of 'overtime' that has a duration of -2. This way the total for the day shows 8 hours, which means the resource has completed their time for the day. We do not need any actuals to be generated on any project.