/**
 * ROWS UNDER A DAY — the one fold of a set into days, for `Timeline` and `CalendarAgenda`. The day
 * head stays with each device.
 */
export interface DayRun<T> {
    /** An ISO date, so runs sort as text. */
    day: string;
    rows: readonly T[];
}
/**
 * Ascending, each day's rows in `order`. A `null` day is dropped. Ties break on arrival; sorts run
 * over copies.
 */
export declare function dayRuns<T>(rows: readonly T[], day: (row: T) => string | null, order?: (a: T, b: T) => number): DayRun<T>[];
/**
 * Local, never `toISOString`, which is UTC and files pre-07:00 events east of Greenwich under the
 * previous day.
 */
export declare function dayKey(date: Date): string;
/**
 * Every day of a window, inclusive, so a register whose rows are days draws the gaps it is read
 * for. Empty when an end is not a date or the window is inverted. Walked at noon so a DST step
 * lands on the next day.
 */
export declare function calendarDays(from: string, to: string): string[];