It is time to prepare for CSS exams.

It is time for CSS exams to be prepared

It was time for CSS exams to be prepared

It should be time for CSS exams to be prepared

It will be time for CSS exams to be prepared

All of the above

Active Voice = Subject + verb + Noun/Pronoun + to + first form of a verb + Object.

Passive Voice = Subject + verb + Object + to be + third form of a verb + by + noun.