We may, therefore, assume that in the Greek-speaking Jewish community of Rome, σάββατα σαββάτων, “the Great Sabbath,” was the common designation—or at least a familiar designation—of the Day of Atonement. In that case it could scarcely be otherwise than familiar to those who had any dealings whatever with the Jews. Fuscus pretends to share a very general observance, and on the strength of it to be disinclined to discuss any personal matters with his friend. Can that day have been a simple Sabbath? The tone indicates a rarer and more solemn occasion. Besides, we are definitely told that it is a special Sabbath, the “thirtieth.” The Jews at that time seem to have reckoned their festivals by strict lunar months (Josephus, Ant. IV. x.) and their civil year by the Macedonian calendar. The thirtieth Sabbath, if we reckon by the Roman calendar, might conceivably have fallen on the Atonement. By the Macedonian or Athenian it could not have done so. However, as the Roman calendar was a solar one, the correspondence of the thirtieth Sabbath with the Atonement can only have been a fortuitous one in a single year. _Tricesima sabbata_ can hardly apply to that. It is just possible that the reason for the word “thirtieth” is to be found in the widely and devoutly pursued astrology of that time. The number thirty had a certain significance in astrology, Firmicus Maternus, IV. xvii. 5; xxii. 3. If for one reason or another the _mansio_ of the moon, which coincided with the second week of the seventh lunar month (cf. Firm. Mat. IV. i. seq. for the importance of the moon in astrology), bore the number thirty, then _tricesima sabbata_, to initiated and uninitiated, might bear the portentous meaning required for the Horatian passage. Whether that is so or not, the only Sabbath which we know to have been specially singled out from the rest of the year, was this σάββατα σαββάτων, the Day of Atonement. Whatever reason there was for calling it the thirtieth, the mere fact of its being particularly designated makes it likely that Horace referred to that day.