/**
 * Timezone boundary helpers — internal.
 *
 * Both functions read an ISO instant in a given IANA timezone and project it
 * onto the wall clock of that zone. They use Intl.DateTimeFormat with
 * hourCycle: 'h23' to avoid 12/24-hour ambiguity. Used internally by the
 * timetable model and `groupItemsByDate`; not exported from the package's
 * public surface.
 */
/**
 * Local minute-of-day [0, 24*60) for an ISO instant in the given zone.
 * Returns NaN if the inputs cannot be parsed (caller should drop the item).
 */
export declare function getLocalMinuteOfDay(isoTimestamp: string, timeZone: string): number;
/**
 * Local YYYY-MM-DD for an ISO instant in the given zone.
 * Returns null if the inputs cannot be parsed.
 */
export declare function getLocalDateKey(isoTimestamp: string, timeZone: string): string | null;
