As of what date are trailers and converter dollies required to be equipped with ABS?

AAMVA CDL Manual, Section 6.3.1, p. 6-7

Knowing the distinct ABS-required dates for tractors versus trailers and dollies helps a driver correctly identify whether a piece of equipment should have ABS at all. Mixing up the tractor date with the trailer/dolly date is a common and testable error.