In a UTC server or serverless runtime, new Date("YYYY-MM-DD") is UTC midnight and renders as the previous day in western timezones. Parse date-only strings into explicit local components (new Date(y, m-1, d)) anywhere a date becomes a display string or a day-of-week. Triggers when parsing a date-only string server-side or computing a printed day from one. Does not fire on full ISO timestamps carrying explicit timezones.
