Despite the computations by Yose ben Halafta, confusion persisted for a long time as to how the calculations should be applied. During 1000, for example, the Muslim chronologist al-Biruni noted that three different epochs were used by various Jewish communities being one, two, or three years later than the modern epoch. The epoch seems to have been settled by 1178, when Maimonides, in his work "Mishneh Torah", described all of the modern rules of the Hebrew calendar, including the modern epochal year. His work has been accepted by Jews as definitive, though it does not correspond to the scientific calculations. For example, the Jewish year for the destruction of the First Temple has traditionally been given as 3338 AM or 421/2 BC. This differs from the modern scientific year, which is usually expressed using the Proleptic Julian calendar as 587 BC. The scientific date takes into account evidence from the ancient Babylonian calendar and its astronomical observations. So, too, according to Jewish computation, the destruction of the Second Temple occurred in the lunar month of Av in "anno" 68 AD, rather than in 70 AD. In this and related cases, a difference between the traditional Jewish year and a scientific date in a Gregorian year or in a proleptic Julian calendar date results from a disagreement about when the event happened—and not simply a difference between the Jewish and Gregorian calendars (See the "Missing Years" in the Jewish Calendar and below, "Excursus: Jewish Chronology in the Scroll of Antiochus").