declare type Weekday = Date;
declare type Weekend = Date;

export const isDate = (val: unknown): val is Date =>
  val instanceof Object && val.constructor === Date;

export const isWeekday = (val: unknown): val is Weekday =>
  isDate(val) && val.getDay() % 6 !== 0;

export const isWeekend = (val: unknown): val is Weekend =>
  isDate(val) && val.getDay() % 6 === 0;