[Answered ]-First form required in formset

Try min_num and validate_min like this –

form_class =  modelformset_factory(EventTime, form = EventTimeForm, extra=3, formset=EventTimeFormset, min_num=1, validate_min=True)

This will automatically validate for at least one formset factory item.

Documented here –

https://docs.djangoproject.com/en/1.9/topics/forms/formsets/#validate-min