code: public long set(long instant, int value) {
          FieldUtils.verifyValueBounds(this, value, iMin, iMax);
          return super.set(instant, value - iOffset);
      }
docs: Set the specified amount of offset units to the specified time instant.
  
  @param instant  the time instant in millis to update.
  @param value  value of units to set.
  @return the updated time instant.
  @throws IllegalArgumentException if value is too large or too small.