Change into passive voice: It is time to buy books.

Explanation:
In order to change the given sentence into passive voice, we need to identify the subject, verb, and object of the sentence.

The subject of the sentence is "It" and the verb is "is". The object of the sentence is "time to buy books".

To convert the sentence into passive voice, we need to make the object the subject and the subject the object of the sentence. The verb "is" will be changed to "are" to maintain the correct tense.

Therefore, the passive voice sentence will be:

Books need to be bought.

Explanation:
The original sentence "It is time to buy books" has been changed into passive voice as "Books need to be bought."

The subject "Books" has become the new subject of the sentence, and the verb "need to be bought" is in passive voice. In the passive voice construction, the object "books" becomes the subject, and the verb "need to be bought" indicates the action being done to the subject.

The passive voice construction emphasizes the action of buying books rather than the time aspect mentioned in the original sentence. It suggests that there is a need or requirement for the books to be purchased.

The passive voice is often used when the focus is on the action or when the doer of the action is unknown or unimportant. In this case, the emphasis is on the books and the necessity of their purchase.

Books are to be bought this time.