/**
 * Convert ISO date string to Date object
 *
 * @param dateString - ISO 8601 date string (YYYY-MM-DD or full ISO timestamp)
 * @returns Date object
 *
 * @remarks
 * - Accepts both date-only (YYYY-MM-DD) and full ISO timestamps
 * - Date-only strings are parsed as UTC midnight to avoid timezone issues
 * - Full timestamps preserve timezone information
 *
 * @throws {Error} If dateString is invalid or cannot be parsed
 *
 * @example
 * ```typescript
 * // Date-only (parsed as UTC midnight)
 * const date1 = iso('2024-01-15'); // 2024-01-15T00:00:00.000Z
 *
 * // Full timestamp
 * const date2 = iso('2024-01-15T14:30:00Z'); // 2024-01-15T14:30:00.000Z
 * const date3 = iso('2024-01-15T14:30:00+02:00'); // With timezone offset
 * ```
 */
export declare function iso(dateString: string): Date;
/**
 * Get current date as ISO string (YYYY-MM-DD)
 *
 * @returns ISO date string in YYYY-MM-DD format
 *
 * @example
 * ```typescript
 * const today = isoToday(); // '2024-01-15'
 * ```
 */
export declare function isoToday(): string;
/**
 * Add days to an ISO date string
 *
 * @param dateString - ISO date string (YYYY-MM-DD)
 * @param days - Number of days to add (can be negative)
 * @returns New ISO date string (YYYY-MM-DD)
 *
 * @example
 * ```typescript
 * const tomorrow = addDays('2024-01-15', 1); // '2024-01-16'
 * const yesterday = addDays('2024-01-15', -1); // '2024-01-14'
 * ```
 */
export declare function addDays(dateString: string, days: number): string;