/** Stable date key for Map lookups (avoids string allocation per isSameDay). */
export declare function getDateKey(date: Date): string;
export declare function parseEventDate(date: Date | string): Date;
export declare function getEventHour(date: Date | string): number;
export declare function getEventDuration(start: Date | string, end?: Date | string): number;
export declare function formatHour(hour: number): string;
/** Build a grid of weeks for a month calendar. Returns array of 7-day week arrays. */
export declare function buildCalendarGrid(referenceDate: Date, weekStartsOn: 0 | 1 | 2 | 3 | 4 | 5 | 6): Date[][];
