1. A schedule management apparatus for managing user's schedules and tasks, comprising: a context estimation rule storage device which stores a context estimation rule for use in estimation of contexts indicative of conditions of the user; a listing device configured to list up spare time blocks wherein there is no schedule set by the user; a context estimation device configured to apply the context estimation rule to the listed spare time blocks, thereby estimating contexts of the spare time blocks; a task template storage device which associates a task with subtasks of the task, and stores a task template showing respective metadata of the subtasks; a task input device which inputs a task; a dividing device configured to divide the task input by the task input device into plural subtasks on the basis of the task template; a task recommendation rule storage device which stores a task recommendation rule for recommending tasks to do in accordance with the relation between contexts and metadata of tasks; a task recommendation device configured to apply the task recommendation rule to the listed spare time blocks, and to recommend tasks to do in the spare time blocks on the basis of the contexts of the spare time blocks and the metadata of the subtasks; and a task schedule management device configured to manage recommended tasks as schedules.