1) This form can be used as command. Children arrive on time for class. (repeated action) Children must arrive on time for class. (command) Children are to arrive on time for class. (command) The room is cleaned on Fridays. (repeated action) The room must be cleaned on Fridays. (command) The room is to be cleaned on Fridays. (command) 2) This form can be used with a future meaning and with a future-in-the-past meaning. 2a) Future The room will be cleaned tomorrow. The room is going to be cleaned tomorrow. The room is to be cleaned tomorrow. = The room is planned/supposed to be cleaned tomorrow. 2b) Future in the past The manager said that the room would be cleaned the next day. ("would be cleaned" = past version of "will be cleaned") The manager said that the room was going to be cleaned the next day. ("was going to be cleaned" = past version of "is going to be cleaned") The manager said that the room was to be cleaned the next day. ("was to be cleaned" = past version of "is to be cleaned")

This construction is called the passive infinitive.

This is the passive voice. It is often used when services are being done for you. It is also used when the actor is unknown or unimportant. I was robbed. My car was fixed this morning. I had my hair done at Susie's Salon.