I assume you have Time Management integrated with Project Managment and submiting time against the tasks of a project with the help of Timesheets.
Plesae note that -
For projects that are integrated with HP Time Management after users enter actual effort for tasks on the
Time Breakdown tab, the time sheet update service (TM-PM Sync) sends updates of that actual effort to the project work plans for those tasks, as often as specified by the service (by default, every 3 hours).
We are running on 12 Hour cycle - this is due to the large number of users using timesheet. May not be any soon, but I guess it would hurt the performance of whole application in future if you take it down to 5 mins!