import { DurationInput } from './types';
/**
 * Returns `true` if a duration is negative overall.
 *
 * Note, this function performs implicit normalization, so ambiguous
 * units, like months, work with average values.
 *
 * @example
 * isNegative('P-1D') // true
 * isNegative({ days: 1, hours: -25 }) // true
 * isNegative({ days: 1, hours: -23 }) // false
 */
export declare const isNegative: (duration: DurationInput) => boolean;