Websites read the timezone of the remote browser, not that of your local automation process. Managed proxy sessions align the browser timezone and locale with the verified egress where the transport supports that configuration.
For a deliberate page-level override, connect to the session over CDP and set an IANA timezone before navigation:
// client is an already connected, page-scoped CDP session.
await client.send("Emulation.setTimezoneOverride", {
timezoneId: "America/Chicago"
});
Apply the override to each page you control. An emulation setting does not change the actual egress country or attest a browser identity.
See Create a browser session and the Browsers API for authentication, request fields, and limits.