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 of spare time blocks, wherein the context estimation rule is used to generate a context by applying the context estimation rule to the spare time blocks and the context estimation rule generates contexts corresponding to schedule types before spare time blocks whose contexts are estimated, and wherein the generated context varies based on dates and times of the spare time blocks and the generated context indicates conditions of the user; a listing device configured to list spare time blocks when 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 stores a task template that represents tasks and subtasks associated with the tasks, the task template including 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 the associated subtasks based on 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; a task schedule management device configured to manage recommended tasks as schedules; and a computer processor that executes the schedule management apparatus.