A method of creating, by a computer, a task plan that prescribes an execution time of a task on which a completion time limit is set, the method comprising:
- allocating the execution time of at least one first task in a first period;
- calculating a first total time length for execution of the at least one first task allocated in the first period;
- identifying at least one second task that is not allocated in the first period and has the completion time limit set in the first period;
- calculating a second total time length for execution of the at least one second task;
- and
- displaying the first total time length and the second total time length on a display device.