What role does the infinitive phrase play in sentence Julius most lasting reform was to set up a new calendar?

In the sentence "Julius' most lasting reform was to set up a new calendar," the infinitive phrase "to set up a new calendar" functions as a predicate nominative.

Here's why:

* Predicate Nominative: A predicate nominative is a noun or pronoun that follows a linking verb (like "was" in this case) and renames or identifies the subject of the sentence.

* Subject: The subject of the sentence is "Julius' most lasting reform."

* Linking Verb: The linking verb is "was."

* Infinitive Phrase: The infinitive phrase "to set up a new calendar" acts as the predicate nominative, renaming or identifying the subject, "Julius' most lasting reform."

Therefore, the infinitive phrase tells us what Julius' most lasting reform *was*.