For what it's worth, I've had this happen to me persistently on Firefox, but it went away a few months ago and I haven't thought much of it since. I figured it might be related to how certain configurations of Firefox attempt to do fingerprint resistance, and maybe the browser was (erroneously?) spoofing the timezone. In any event, it's not an issue for me on the latest versions of Firefox and I've never run into it on any other browser.