Controlled by the DATA_MODE environment variable.
Applies to the economic calendar and Market Pulse timeline. Market session status always uses exchange time (America/New_York) regardless of this setting.
Watchlists, alerts, saved screens, and this timezone preference are stored in this browser (localStorage), so they work immediately without an account and never leave your device.
Account sign-in (email/password and OAuth) is wired up server-side via NextAuth and the Prisma schema in prisma/schema.prisma, ready to sync this data to Postgres once DATABASE_URL is configured for production. See the README for setup steps.