serializers.py

class EmberDateField(serializers.DateField):

    def to_internal_value(self, value):
        value = value.split('T', 1)[0]

        return super().to_internal_value(value)

    def to_representation(self, value):
        res = super().to_representation(value)
        #  XXX This is a hack - assumes CET timezone, which is 1 hour
        # later than UTC. CET gets stored as 'day before 23:00' so we
        # need to restore that part again
        return res + 'T23:00:00.000Z'