Rabbi Pinchas ben Yair is placed in the second century CE only by his standing as a Mishnaic-era tanna and as the son-in-law of Rabbi Shimon bar Yochai, whose own circle is conventionally dated to the middle of the century. No chronicle or inscription independent of the Mishnah's generational framework fixes an actual birth or death year.
What would resolve this A datable document or independent notice fixing a year in Rabbi Pinchas ben Yair's life, distinct from the Mishnah's generational placement of his teaching.
OpenTalmudic chronology, history of the Mishnaic periodJacob Neusner, trans., The Mishnah: A New Translation