import type { DurationUnit } from "./durationUnit";
/**
 * Adds a duration to a date and returns a new Date.
 * Calendar-aware for "M" (months) and "y" (years), so end-of-month
 * is preserved (e.g. Jan 31 + 1 month = Feb 28/29).
 *
 * @param {Date} date - Base date
 * @param {number} amount - Amount to add (can be negative)
 * @param {DurationUnit} unit - Unit of the amount
 * @returns {Date} A new Date with the duration added
 * @example
 * addDuration(new Date("2025-01-31"), 1, "M"); // 2025-02-28
 * addDuration(new Date("2025-01-01"), 7, "d"); // 2025-01-08
 */
export declare const addDuration: (date: Date, amount: number, unit: DurationUnit) => Date;