/**
 * Shared period key formatting for time-bucketed analysis tools.
 */
/**
 * Generate a complete range of period keys between two dates.
 * Useful for detecting periods with zero activity (droughts).
 */
export declare function generatePeriodRange(startDate: string, endDate: string, granularity: string): string[];
export declare function formatPeriodKey(dateStr: string, granularity: string): string;