Mark; the appearance of this topic follows a brief exchange on GMF; evidently Duane has experienced something similar. I first noticed it last weekend when a onetime Yahoo Group enlisted all its members on to a new Group on Groups.io without dragging all the historical impedimenta with it.
I suspect the problem will only be apparent to members not on Pacific Time. I (and almost all the others on the new Group) am in the UK, and thus on UTC, or more correctly at the moment UTC + 1.
The time display for incoming messages is correct. However, if I (and I assume anyone else) quotes from a previous post then the time shown for that previous post is exactly (minus) 8 hours different, i.e. Pacific Time.
Duane is of the view that this may an artifact of the work done recently on Date Formats; I don't know enough to either agree or disagree with that statement!
Any chance you can have a look at this sometime?