The "calendar He instructed" was given to the Mosaic authorities in antiquity—the actual 19-year lunar cycle that Meton published years later.

Those that sit in Moses' seat include Hillel II. The calendar was always done via calculation first. Calculation is the basis of the celestial bodies that govern time. Proof of this is found in the fact that, in the diaspora, the Jews have had to follow an exclusively calculated calendar, as there was no land to "observe barley in the coordinates of Israel" for those not remotely near it.

Observation of a maturing crop like barley in the locale of Israel was always done as a verification process anyway.