get weekdayShort() {
    return this.isValid ? Info.weekdays("short", { locObj: this.loc })[this.weekday - 1] : null;
  }
Get the human readable short weekday, such as 'Mon'.
Defaults to the system's locale if no locale has been specified
@example DateTime.local(2017, 10, 30).weekdayShort //=> Mon
@type {string}