# getSubtaskDates

### Description

@short: Calculates the combined start/end dates of tasks nested in a project or another task

@signature: getSubtaskDates: (task_id?: string | number) =\> any

### Parameters

- `task_id` -	(optional) *string | number*	-	the task's id, [root_id](api/config/root_id.md) will be used if not specified

### Returns
- ` dates` - (object) - an object containing the <b>start_date</b> and <b>end_date</b> properties

### Example

~~~jsx
// duration of the whole project
let dates = gantt.getSubtaskDates();
const dateToStr = gantt.templates.task_date;
    
console.log(`${dateToStr(dates.start_date)} - ${dateToStr(dates.end_date)}`);

// duration of the subproject
dates = gantt.getSubtaskDates(1);
    
console.log(`${dateToStr(dates.start_date)} - ${dateToStr(dates.end_date)}`);
~~~

### Details

The method returns an object containing the start date of the earliest subtask and the end date of the latest subtask.

The return object has the following format:

~~~js
{
  start_date: Date|null,
  end_date: Date|null
}
~~~

If a Gantt chart has any scheduled tasks, both properties will have date values. If the Gantt chart is empty or contains only unscheduled tasks, both properties will have `null` values.

### Related API
- [getSubtaskDuration](api/method/getsubtaskduration.md)
- [getTaskBy](api/method/gettaskby.md)