Hillel II

…unity of Israel, the patriarch Hillel II, in 358/359, published the “secret” of calendar making, which essentially consisted of the use of the Babylonian 19-year cycle with some modifications required by the Jewish ritual.

…leading talmudic academy in Babylonia—Hillel II, a Palestinian patriarch, introduced a fixed and continuous calendar in 359 ce. A summary of the regulations governing the present calendar is provided by Maimonides, the great medieval philosopher and legal scholar, in his Code: Sanctification of the New Moon, chapters 6–10.

…approximately 359 by the patriarch Hillel II, and this, coupled with the widespread presence of rabbis, ensured the continuity of Jewish adherence. Even the restrictions on synagogal worship and preaching imposed by the Eastern emperor Justinian I (reigned 527–565) apparently had no devastating effect. A new genre of liturgical poetry,…