docs: @Restricted(NoExternalUse.class)
      public static long daysBetween(@Nonnull Date a, @Nonnull Date b){
          LocalDate aLocal = a.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
          LocalDate bLocal = b.toInstant().atZone(ZoneId.systemDefault()).toLocalDate();
          return ChronoUnit.DAYS.between(aLocal, bLocal);
      }