If we translate to match the tenses and moods in the Italian (present indicative in the first clause and present subjunctive in the second), we'd end up with "Maybe it is time that I enter (join) the game." Entered would be past subjunctive.
"Maybe it is time for me to join in the game" was not accepted 10 Aug 17. Is this because of the "in", which in retrospect feels superfluous? Because joining a game feels more idiomatic than entering one.