Skald:
Another variable to consider ... does the issue only affect users who use more than one device ?
Unsure, on that one. I know that where I
see saw the issue is on my desktop (and just so we stay on topic, it was the same problem as the OP - not ALL of the timestamps in all locations within RPoL were displaying the SAME time stamp - not a case of whether or not that timestamp is "proper". In my particular case, where I really noticed it was in the Cast List, because Last Post times there wouldn't necessarily match up with the time in the thread or on the front page.)
...but I was seeing the issue on my desktop since long before I started ALSO using my phone to do RPoL things. So in theory, at one time, I did see the issue while only using one device. (My phone never had the issue, but I just chalked that up to the phone auto-updating itself better.)
However...and incredibly amusingly, I realized while writing out this entire post that I no longer have the issue. Every page location on RPoL is now displaying the same time for me, and all post times match up across all pages. (I don't actually care whether or not it's correct for DST, but it appears to be.) This is new, although I'm not sure HOW new, because it's not something I pay that much attention to. A few months ago, I know the issue was there. Now it isn't. I've been in the habit of checking player times against my GM times for so long, I couldn't tell you when the timestamps "fixed" themselves. But they have.
For whatever it's worth, I had both a browser (Chrome) and OS (Win10) update in the past few days. /shrug