/**
 * Retrieves the day of the year from a given date.
 *
 * @example
 * dayOfYear("2024-01-01") // 1
 * dayOfYear("2024-12-31") // 366 (leap year)
 *
 * @param date The date to retrieve the day from. Defaults to the current date.
 * @returns The day of the year (1-366).
 */
export declare function dayOfYear(date?: Date | string | number | null): number;