WordPress Timezone Problems

Hello ??
I am working on setting up a self-hosted WordPress blog, and am running into some problems:

1) Changing the timezone setting does not change the displayed time of existing posts/comments
2) When I use O in a time format (ie, the timezone offset) or any other timezone-displaying format it shows my server timezone instead of my set timezone
3) When I use U to output a unix timestamp it outputs in such a way that it is off from UTC by the difference between my set timestamp and my server timestamp

Some thoughts by others are found here (https://gregcerveny.com/20061129/wordpress-times-time-zones-and-daylight-savings/) and more importantly here: (https://www.makeyougohmm.com/20070125/4178/)