diff --git a/models/workflow/workflow_mongo_accessor.go b/models/workflow/workflow_mongo_accessor.go
index 89600d1..0abfc57 100644
--- a/models/workflow/workflow_mongo_accessor.go
+++ b/models/workflow/workflow_mongo_accessor.go
@@ -28,20 +28,23 @@ func (wfa *WorkflowMongoAccessor) execution(realData *Workflow, delete bool) (in
 	}
 	if realData.Schedule != nil {
 		accessor := (&workflow_execution.WorkflowExecution{}).GetAccessor()
-		if realData.Schedule.Start.IsZero() {
+		if realData.Schedule.Start == nil || realData.Schedule.Start.IsZero() {
 			return 422, errors.New("should get a start date on the scheduler.")
 		}
+		if realData.Schedule.End != nil && realData.Schedule.End.IsZero() {
+			realData.Schedule.End = nil
+		}
 		if len(realData.Schedule.Cron) > 0 {
-			if realData.Schedule.End.IsZero() {
+			if realData.Schedule.End == nil {
 				return 422, errors.New("a cron task should got a end date.")
 			}
 			c, err := cron.Parse(realData.Schedule.Cron)
 			if err != nil {
 				return 422, errors.New("Bad cron message: " + err.Error())
 			}
-			for s := c.Next(realData.Schedule.Start); !s.IsZero() && s.Before(realData.Schedule.End); s = c.Next(s) {
+			for s := c.Next(*realData.Schedule.Start); !s.IsZero() && s.Before(*realData.Schedule.End); s = c.Next(s) {
 				obj := &workflow_execution.WorkflowExecution{
-					ExecDate:   s,
+					ExecDate:   &s,
 					EndDate:    realData.Schedule.End,
 					State:      workflow_execution.SCHEDULED,
 					WorkflowID: realData.UUID,
diff --git a/models/workflow/workflow_schedule.go b/models/workflow/workflow_schedule.go
index 97e126a..32c61fb 100644
--- a/models/workflow/workflow_schedule.go
+++ b/models/workflow/workflow_schedule.go
@@ -3,10 +3,10 @@ package oclib
 import "time"
 
 type WorkflowSchedule struct {
-	Id    string    `json:"id"`
-	Start time.Time `json:"start" bson:"start" validate:"required"`
-	End   time.Time `json:"end,omitempty" bson:"end,omitempty"`
-	Cron  string    `json:"cron,omitempty" bson:"cron,omitempty"`
+	Id    string     `json:"id"`
+	Start *time.Time `json:"start" bson:"start" validate:"required"`
+	End   *time.Time `json:"end,omitempty" bson:"end,omitempty"`
+	Cron  string     `json:"cron,omitempty" bson:"cron,omitempty"`
 }
 
 func (ws *WorkflowSchedule) GetAllDates() (timetable []time.Time) {
diff --git a/models/workflow_execution/workflow_execution.go b/models/workflow_execution/workflow_execution.go
index 3598d51..a8f5560 100644
--- a/models/workflow_execution/workflow_execution.go
+++ b/models/workflow_execution/workflow_execution.go
@@ -39,8 +39,8 @@ func (d ScheduledType) EnumIndex() int {
 
 type WorkflowExecution struct {
 	UUID       string        `json:"id,omitempty" bson:"id,omitempty" validate:"required"`
-	ExecDate   time.Time     `json:"execution_date,omitempty" bson:"execution_date,omitempty" validate:"required"`
-	EndDate    time.Time     `json:"end_date,omitempty" bson:"end_date,omitempty"`
+	ExecDate   *time.Time    `json:"execution_date,omitempty" bson:"execution_date,omitempty" validate:"required"`
+	EndDate    *time.Time    `json:"end_date,omitempty" bson:"end_date,omitempty"`
 	State      ScheduledType `json:"state,omitempty" bson:"state,omitempty" `
 	WorkflowID string        `json:"workflow_id" bson:"workflow_id,omitempty"`
 }