You should check out Ladybird browser, it’s an impressive piece work, it’s definitely no ready for everyday use, but it is proof that a small community can develop and maintain a project as complex and large as a browser.
It is probably the only browser in active development that is not being paid by Google, even Firefox gets most of its income from defaulting the search engine to Google
Thats an issue with the time library, not with timestamps. Actually timestamps are always in UTC, you need to do the conversion to your local time when displaying the value. There should be no possible off-by-one errors, unless you are doing something really wrong.