what is the best way to achieve the following:

export interface Iabc {
   startDate: Date | string | null;
   endDate: Date | string | null;
   nestedSection: {
      a: string | null;
      b: boolean | null;
      c: boolean | null;
      d: Date | string | null;
   };
}

Currently I am converting the Dates contained in the nested sections like so

 nestedSection: Object.entries(values.nestedSection).reduce((prev, [k, v]) => {
                  if (v instanceof Date) {
                     return {
                        ...prev,
                        [k]: moment(v).format('YYYY-MM-DD'),
                     };
                  }
                  return prev;
               }, values.nestedSection),

However I need to do it for startDate and endDate a level up from the nested section. TIA