What is the use the settlementDate argument in PiecewiseFlatForward?

Posted by ago-2 on
URL: http://quantlib.414.s1.nabble.com/What-is-the-use-the-settlementDate-argument-in-PiecewiseFlatForward-tp4588.html

The settlement date, as I learn (thanks Luigi), is set by
Settings.instance().evaluationDate()

So what is the use of the settlementDate argument in PiecewiseFlatForward?