[Fixed]-Saving a Date in a Coisefield – Django?

I would do it as two fields:

#models.py
class Event(models.Model):     
         start = models.DateTimeField(default=datetime.now())
         end = models.DateTimeField()

and for calendar (=widget) i would use this or some similar plugin:
https://github.com/nkunihiko/django-bootstrap3-datetimepicker