QML Date set problem

[lqsa]

In this code:

import QtQuick 2.0
import QtQuick.Controls 1.4
 
Item {
    id: root
    property date value: new Date(2000, 0, 1)
    Button {
        onClicked: {
            root.value.setFullYear(2001)
            console.log(root.value)
        }
    }    
}

import QtQuick 2.0
import QtQuick.Controls 1.4

Item {
    id: root
    property date value: new Date(2000, 0, 1)
    Button {
        onClicked: {
            root.value.setFullYear(2001)
            console.log(root.value)
        }
    }    
}

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When push the button, why date doesn't change? On the log appears 2000, not 2001