-- Each user's IANA time zone (e.g. 'America/Los_Angeles').
-- Captured from the browser on login/signup; everything date-based
-- (streaks, "today", journal entries, recitation log) uses this so
-- a Pacific user logging at 11pm doesn't bleed into UTC's tomorrow.
ALTER TABLE users
    ADD COLUMN timezone VARCHAR(64) NOT NULL DEFAULT 'UTC' AFTER email;
