> > shouldn't dates in square brackets always be sorted (ascending, oldest to newest)?
> No, there isn't any such requirement.
Dates in square brackets may contain seasons and (and as we made clear last
year) seasons within the same year cannot be sorted. Which of spring or automn
comes first within year 2012 depends on which place on the earth you consider.
Of course, we could decide to sort dates within square brackets if none of them
contains any season (for example), but I do not consider this a requirement.