It's difficult to say just when late becomes too late. But although spring bulbs are best planted early, as long as the soil is still workable, you can continue planting right through November and even into early December.
Dig a hole two or three times as deep as the bulb's diameter, and position the bulb root-end down. Cover with soil and water well. It is always great to put in the hole a slow release fertilizer plus bone meal.