It does this seemingly by subtracting one from the year, making it positive, then (I infer) appending "BC" to the result. Thus for the year "-1" it yields "0002-01-01 BC"
/* * There is no 0 AD. Years go from 1 BC to 1 AD, so we make it * positive and map year == -1 to year zero, and shift all negative * years up one. For interval years, we just return the year. */
The code comment took me a bit to process - seems like the following would be better (if its right - I don't know why interval is a pure no-op while non-interval normalizes to a positive integer).
Years go from 1 BC to 1 AD, so we adjust the year zero, and all negative years, by shifting them away one year, We then return the positive value of the result because the caller tracks the BC/AD aspect of the year separately and only deals with positive year values coming out of this macro. Intervals denote the distance away from 0 a year is so we can simply take the supplied value and return it. Interval processing code expects a negative result for intervals going into BC.
