There should be a way to track time against every Task and Subtask through start/stop timers and manual time entries. Users should also be able to define time estimates, compare estimated time against actual time spent, and mark entries as billable or non-billable.

Additionally, the system should support user-wise timesheets and time-tracking reports with filters across users, clients, Spaces, Lists, and date ranges.

This will enable users to track productivity, monitor time spent across projects, measure estimates versus actuals, and gain better visibility into resource utilization and billable hours.