Ok, i need help on this. Im doing a some problems in my school and i am required to "underline the infinitive in the sentance, and write whether its being used as a "Noun" Adjective" or Adverb" here is one of the sentences

Its time to go home.

Well i know that the infinitive is "To Go" BUT! the answer key tells me that "To go" is being used as a Adjective. How is that? i know that an adjective is used to tell, Which one? What kind of? and how many? (and whose.) But i cant understand how those are being asked of in the infinitive "To Go" Please help. Thanks. :-)