According to this calculation, the Romans destroyed the Temple in ad 68. Rabbinic chronology is at odds with the accepted conventional chronology which establishes the date as ad 70. Scholars differ by one or two years. From ad 70 until now, both Rabbinic and conventional chronologies agree. But the real difference is the length of the Persian Conquest.
Most scholars agree with the conventional chronology.
This is conventional chronology, not Rabbinic chronology. According to Rabbinic chronology, Persian rule until the destruction of the Second Temple in ad 70 spans 420 years. According to conventional chronology it is 590 years. There is a difference of 170 years between conventional chronology and Rabbinic chronology. If we add the difference to Rabbinic chronology the Jewish year will not be 5760 but 5930.