Tasks created using PSI has incorrect duration

Hi,

I'm using the following code to create projects tasks within workflow using PSI. The start date and end date that I'm using to create tasks are "Start Date: 8/7/2012" and "End Date: 8/15/2012" so the duration will be 7 days but when I go to the project schedule, the end date will be "8/14/2012" which makes the duration 6 days.

What is wrong with that:

	Dim projectClient As SvcProject.ProjectClient = WorkflowHelper.PSIProxy.GetProjectClient(wfContext.Site.Url)
        Dim projectDataSet As SvcProject.ProjectDataSet = projectClient.ReadProject(projectSequence1.WorkflowContext.ProjectUid, SvcProject.DataStoreEnum.WorkingStore)
        Dim newProjectDataSet As New SvcProject.ProjectDataSet

        If projectDataSet.Task.Rows.Count = 1 AndAlso DelivrablesXML(0) IsNot Nothing AndAlso String.IsNullOrEmpty(DelivrablesXML(0).ToString()) = False Then


            Dim sessionUID As Guid = Guid.NewGuid()
            
            projectClient.CheckOutProject(projectSequence1.WorkflowContext.ProjectUid, sessionUID, "Settings Project Delivrables in session " + sessionUID.ToString())

            Dim jsSerializer As New System.Web.Script.Serialization.JavaScriptSerializer

            Dim arr As Object() = CType(jsSerializer.DeserializeObject(DelivrablesXML(0)), Object())

            If arr IsNot Nothing Then

                For Each a As Dictionary(Of String, Object) In arr

                    Dim newTask As SvcProject.ProjectDataSet.TaskRow = newProjectDataSet.Task.NewTaskRow

                    Dim startDate As Date = CDate(a("StartDate"))
                    Dim endDate As Date = CDate(a("EndDate"))

                    newTask.TASK_NAME = a("Name").ToString()
                    newTask.TASK_START_DATE = New DateTime(Year(startDate), Month(startDate), Day(startDate), 8, 0, 0)
                    newTask.TASK_FINISH_DATE = New DateTime(Year(endDate), Month(endDate), Day(endDate), 8, 0, 0)
                    newTask.TASK_DUR = 33600
                    'newTask.TASK_IS_MILESTONE = True
                    newTask.TASK_DUR_FMT = Microsoft.Office.Project.Server.Library.Task.DurationFormat.Day
                    newTask.TASK_CONSTRAINT_TYPE = CShort(Microsoft.Office.Project.Server.Library.Task.ConstraintType.AsSoonAsPossible)
                    newTask.TASK_DUR_IS_EST = True
                    newTask.TASK_LEVELING_DELAY_FMT = CShort(Microsoft.Office.Project.Server.Library.Task.DurationFormat.Day)
                    newTask.TASK_DUR_VAR = 0
                    newTask.TASK_ACT_START = CDate(a("StartDate"))
                    newTask.PROJ_UID = projectSequence1.WorkflowContext.ProjectUid
                    newTask.TASK_UID = Guid.NewGuid()

                    newProjectDataSet.Task.AddTaskRow(newTask)

                Next

                Dim updateJobUID As Guid = Guid.NewGuid()
                
                projectClient.QueueAddToProject(updateJobUID, sessionUID, newProjectDataSet, False)
                WaitForQueue(updateJobUID)
                
            End If

            Dim checkinJobUID As Guid = Guid.NewGuid()
                        
            projectClient.QueueCheckInProject(checkinJobUID, projectSequence1.WorkflowContext.ProjectUid, True, sessionUID, "Settings Project Delivrables in session " + sessionUID.ToString())
            WaitForQueue(checkinJobUID)
            

        End If