Oxidized API delivers a UTC date https://github.com/ytti/oxidized/issues/386 so someone would need to convert it in LibreNMS possibly to the php tz, or feel free to submit a PR.
Oxdized-Web should show correct timezone, and switched from server timezone (zdump /etc/localtime) to the client Browser timezone https://whatismytimezone.com/
This is a community driven project, so unless someone see’s this important enough to solve, then you are either stuck on waiting or could try to code some timezone conversion in and send a pull request.