code: public long set(long instant, int value) {
          FieldUtils.verifyValueBounds(this, value, getMinimumValue(),
                                       getMaximumValueForSet(instant, value));
          return instant + (value - get(instant)) * iUnitMillis;
      }
docs: Set the specified amount of units to the specified time instant.
  
  @param instant  the milliseconds from 1970-01-01T00:00:00Z to set in
  @param value  value of units to set.
  @return the updated time instant.
  @throws IllegalArgumentException if value is too large or too small.