import { WeekDay } from './calendar.types';
/** Parse a Date or parseable string into a Date (throws on invalid). */
export declare function toDate(value: Date | string): Date;
/** Midnight (local) of the given date. */
export declare function startOfDay(date: Date): Date;
/** `YYYY-MM-DD` key in local time. */
export declare function dateKey(date: Date): string;
export declare function addDays(date: Date, days: number): Date;
export declare function addMonths(date: Date, months: number): Date;
export declare function startOfMonth(date: Date): Date;
export declare function startOfWeek(date: Date, weekStartsOn: WeekDay): Date;
export declare function isSameDay(a: Date, b: Date): boolean;
export declare function isSameMonth(a: Date, b: Date): boolean;
/** Fraction (0..1) of the day represented by the time portion of `date`. */
export declare function dayFraction(date: Date): number;