Regarding the year of Jesus' birth, it says in Seder HaDoros (Year 3724) that the year 3724 and the year (3)532 are really the same. What in the world does he mean?
Its in the first column first paragraph...
He is saying that the year 3724 coincides with the end of a 532-year calendrical cycle. This cycle is when the 19-year machzor katan and the 28-year machzor gadol return to their initial positions (19 x 28 = 532). The year 3724 comes after exactly 7 of those cycles (532 x 7 = 3724). He does not explain why this has any significance.