export interface DayParts {
    year: number;
    /** 1 to 12. */
    month: number;
    day: number;
}
export declare function daysInMonth({ year, month }: Pick<DayParts, 'year' | 'month'>): number;
/** The parts of a `'YYYY-MM-DD'` string, or `null` for anything else, 31 February included. */
export declare function parseDay(value: unknown): DayParts | null;
/** `value` itself when it is a `'YYYY-MM-DD'` day that exists, otherwise `null`. */
export declare function asDay(value: unknown): string | null;
export declare function formatDay({ year, month, day }: DayParts): string;
/** The day `date` falls on in the browser's time zone, as `'YYYY-MM-DD'`; `''` for an Invalid Date. */
export declare function dateToDay(date: Date): string;
/** The first moment of a `'YYYY-MM-DD'` day in the browser's time zone. An Invalid Date for anything else. */
export declare function dayToDate(day: string): Date;
/** The `'HH:MM'` of `date` in the browser's time zone, the value a TimeInput holds; `''` for an Invalid Date. */
export declare function dateToTime(date: Date): string;
/**
 * The moment a `'YYYY-MM-DD'` day and an `'HH:MM'` time stand for in the browser's time zone,
 * DatePicker's and TimeInput's values together. A time the clock skips that day resolves forwards
 * (02:30 becomes 03:30), a repeated one to its first occurrence. An Invalid Date for anything else.
 */
export declare function dayTimeToDate(day: string, time: string): Date;