Django DatField returns null value every time I register information

Question

I have a model that registers a project information which have start date and end date but when I submit those information, the value of start date and end date is null their value never saved to the database. Here is my model.py

class Project(models.Model):
    project_name = models.CharField(max_length=255, blank=False)
    created_by = models.ForeignKey(
        Employee, related_name='employee', on_delete=models.CASCADE) 
    status = models.CharField(
        max_length=50, choices=PROJECT_STATUS_CHOICES, default=COMING_STATUS, null=True, blank=True
    )
    start_date = models.DateField( null=False)
    end_date = models.DateField( null=False)
    created_at = models.DateTimeField(auto_now_add=True)
    updated_at = models.DateTimeField(auto_now=True)
    
    def __str__(self):
        return self.project_name

Here is the list of project data

 {
        "id": 1,
        "created_by": "Teshome",
        "project_name": "Teshome",
        "status": "Coming",
        "start_date": null,
        "end_date": null,
        "created_at": "2022-04-15T12:16:31.045887Z",
        "updated_at": "2022-04-15T12:16:31.045887Z"
    },
    {
        "id": 2,
        "created_by": "Teshome",
        "project_name": "Babi",
        "status": "Ended",
        "start_date": null,
        "end_date": null,
        "created_at": "2022-04-15T12:30:03.332208Z",
        "updated_at": "2022-04-15T12:30:03.332208Z"
    }, 

Here is the Django admin interface where I register project information. I did not use any frontend framework to register project information I just did it from Django Admin.

How can I solve this Isuue?

Thanks