src/java.base/share/classes/java/time/Instant.java

*** 756,766 ****
          long dur = unitDur.toNanos();
          if ((LocalTime.NANOS_PER_DAY % dur) != 0) {
              throw new UnsupportedTemporalTypeException("Unit must divide into a standard day without remainder");
          }
          long nod = (seconds % LocalTime.SECONDS_PER_DAY) * LocalTime.NANOS_PER_SECOND + nanos;
!         long result = (nod / dur) * dur;
          return plusNanos(result - nod);
      }
  
      //-----------------------------------------------------------------------
      /**
--- 756,766 ----
          long dur = unitDur.toNanos();
          if ((LocalTime.NANOS_PER_DAY % dur) != 0) {
              throw new UnsupportedTemporalTypeException("Unit must divide into a standard day without remainder");
          }
          long nod = (seconds % LocalTime.SECONDS_PER_DAY) * LocalTime.NANOS_PER_SECOND + nanos;
!         long result = Math.floorDiv(nod, dur) * dur ;
          return plusNanos(result - nod);
      }
  
      //-----------------------------------------------------------------------
      /**