Mark makes some good points.
In American English, as of can basically mean the opposite in two different situations (you just pointed that out, too, George).
"ON, AT, FROM —used to indicate a time or date at which something
begins or ends"
I also know "as of" in the sense of "until." Here's a good post about this:
http://learnersdictionary.com/qa/as-of-todayI quote:
"As of today can mean 'from the beginning up until now, including today,'...On the other hand, it can also mean 'starting today and going forward into the future,'...even has a third meaning, which is less common than the other two. It can mean 'today, only” with the implication that things are likely to change."
Not the same in British English, AFAIK; that's why you see all these posts insisting it's used to indicate the start of something.
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