import { type Timezone } from './timezones.js';
/**
 * Asserts that the given input is a valid timezone name.
 *
 * Note that this may actually allow names beyond what is currently in the exact {@link Timezone}
 * type, because this function checks to see if the given timezone can be used to construct a date,
 * regardless of whether it's in our typed list or not.
 *
 * @category Assertion
 */
export declare function assertValidTimezone(potentialTimezone: string, userMessage?: string | undefined): asserts potentialTimezone is Timezone;
/**
 * Checks that the given timezone is valid.
 *
 * Note that this may actually allow names beyond what is currently in the exact {@link Timezone}
 * type, because this function checks to see if the given timezone can be used to construct a date,
 * regardless of whether it's in our typed list or not.
 *
 * @category Assertion
 */
export declare function isValidTimezone(potentialTimezone: string): potentialTimezone is Timezone;