/**
 * Format bytes into a human-readable string.
 * e.g. 4096 -> "4.0 KB"
 */
export declare function formatBytes(bytes: number): string;
/**
 * Format a Date to "YYYY-MM-DD HH:mm".
 */
export declare function formatDate(date: Date): string;
/**
 * Format a Date to "YYYY-MM-DD_HHmmss" for filenames.
 */
export declare function formatDatetime(date: Date): string;
/**
 * Format a relative time string.
 * e.g. "2 hours ago", "37 days ago"
 */
export declare function formatRelativeTime(date: Date): string;
/**
 * Generate a backup filename from the pattern.
 * Supported placeholders: {hostname}, {date}, {time}, {datetime}, {tag}
 */
export declare function generateFilename(pattern: string, options?: {
    tag?: string;
    date?: Date;
    hostname?: string;
}): string;