import { Temporal } from "@js-temporal/polyfill";
import type { FractionalDigit } from "../../types/index.js";
/**
 * Return the end of the specified date-time `unit` for a given ISO 8601 datetime string.
 *
 * - Returns "" for invalid inputs.
 *
 * @param value ISO 8601 datetime string
 * @param unit Temporal.DateUnit | Temporal.TimeUnit to specify the unit for the end
 * @param optionsArg optional: weekStartsOn ("monday" | "sunday"), fractionalSecondDigits (number)
 * @returns ISO 8601 string representing the end of the specified unit, or "" on invalid input
 *
 * @example endOfDateTime("2024-02-29T12:34:56", "month") // "2024-02-29T23:59:59.999999999"
 * @example endOfDateTime("invalid-date", "month") // ""
 */
export declare function endOfDateTime(value: string, unit: Temporal.DateUnit | Temporal.TimeUnit, optionsArg?: {
    weekStartsOn?: "monday" | "sunday";
    fractionalSecondDigits?: FractionalDigit;
}): string;