Hi,

you can use related fields. Another method you can write a code in create and write methods to update the value.

another_model_obj = self.pool.get('another.model').search(cr, uid, [(condition)])
if another_model_obj:
    another_model_object = self.pool.get('another.model').browse(cr, uid, another_model_obj, context=None)
    another_model_object.date = current_model.date