Set default task time to close of business

Be able to set a default time for all task due.

Currently when we create a task and set the due date the time is preset to the quarter hour for which the task in being created. Meaning, if I have a due date of 8/12 and created the task at 11:12 am the task would be due on 8/12 by 11:15 am. Understandably the user can adjust this time which we'd like to keep, but we'd also like the possibility to set a default time for all task to be completed by.