1. A scheduling apparatus comprising: a first calculator configured to calculate an assignment of plural time slots to an electricity consumer, each of the plural time slots is classified into any of categories comprising a morning slot, a daytime slot, and an evening slot; a storage configured to store a first demand, from the electricity consumer, regarding a requested extent to which the categories associated with the assignment are biased, and a second demand, from the electricity consumer, regarding an extent to which the assigned time slots are continuous, a second calculator configured to calculate an extent to which the categories associated with the assignment calculated by the first calculator are biased and calculate a first evaluation value representing a deviation between the first demand and the extent calculated by the second calculator; and a third calculator configured to calculate an extent to which the time slots assigned to the electricity consumer are continuous based on the assignment calculated by the first calculator, and calculate a second evaluation value representing a deviation between the second demand and the extent calculated by the third calculator, wherein the first calculator calculates the assignment so as to optimize an evaluation function including the first evaluation value and the second evaluation value, and the first calculator includes a generator configured to generate a demand reduction assignment program for the electricity consumer based on the assignment calculated by the first calculator.