EDGAR's acceptanceDateTime ends in "Z" but for 181 of 808 companies the clock is already Eastern, not UTC

This is a data reliability story rather than a finance one, and I doubt the shape of it is unique to this source. The SEC's submissions JSON at data.sec.gov gives every filing an acceptanceDateTime ending in "Z". For a large minority of companies that Z is wrong: the clock in the string is already New York time, not UTC. Read as UTC it puts the filing 4 or 5 hours later than it happened, which in my case was enough to move a row across the 16:00 market close and flip it from intraday to after hours. So I stopped trusting the JSON and re-read the raw SGML header of each submission instead, wher