Hello Ashok,
You will be able to change these dates through Operations' Dates. In the Operations tab select all operations and give your new Scheduled start and Scheduled finish times in the Restrictions screen area under Must Start on and Must Finish On fields (See picture below). When you do this for all operations, the Scheduled start and Scheduled finish values in the Dates screen of Order Header will be automatically updated.
Image may be NSFW.
Clik here to view.
KJogeswaraRao
