/**
 * Formats a date relative to a base date using Intl.RelativeTimeFormat.
 * Picks the largest unit that fits the absolute delta.
 *
 * @param {Date} date - The target date
 * @param {Date} [baseDate=new Date()] - Reference date (defaults to now)
 * @param {string} [locale] - BCP 47 locale tag; uses system locale if omitted
 * @returns {string} Localized relative-time string
 * @example
 * formatRelative(new Date(Date.now() - 3600_000), new Date(), "en"); // "1 hour ago"
 * formatRelative(new Date(Date.now() + 86_400_000), new Date(), "ja"); // "1 日後"
 */
export declare const formatRelative: (date: Date, baseDate?: Date, locale?: string) => string;