In order to create a temperature difference value in degrees Celsius from an expression with empty unit, one needs to specify absoluteValue = false in the withUnit call in order for the offset in the "degC" unit symbol to be discarded.

In most situations, the distinction between absolute and relative quantities is expressed using the absoluteValue-annotation or taken care of automatically by the unit handling system. Further, the unit handling system makes no distinction at all for unit symbols that do not carry an offset, so the vast majority of unit symbols can be used directly for both absolute and relative quantities. Thus, specifying absoluteValue when using withUnit is rarely needed.