You can edit schedules to change the properties, such as the name or the schedule or the start and end dates. You cannot change the start date to a date later than the first task in the schedule, or the end date to a date earlier than the last task in the schedule. You can make changes to an Open or Pending schedule to modify pending tasks. You cannot add, change, or delete tasks in a Closed or Locked schedule. To edit a schedule, you must be the schedule owner or an Administrator.
Edit the schedule. See Manually Creating Schedules.