However, all historical evidence refutes Sacrobosco, including dual dates with the Alexandrian calendar.
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The 13th century scholar Sacrobosco claimed that in the Julian calendar February had 30 days in leap years between 45 BC and 8 BC, when Augustus allegedly shortened February by one day to give that day to the month of August named after him so that it had the same length as the month of July named after his adoptive father Julius Caesar.
a commentary on Solomon Abigdor's Hebrew translation of Sacrobosco's treatise on astronomy, Tractatus de Sphæra, or "Aspectus Circulorum," (Hebrew, "Mar'eh ha-Ofannim"), with an explanation of the difficult passages of the translation according to the reading of his masters of the University of Bologna, and the interpretation he had found in Christian works (Cracow, 1720)