Touch Chart 2 - How to "GroupBy" in month of type "Time"

Question

I want to GroupBy in month type: 'Time'.
Like Jan,Feb... A non-repeated month data This is what I have so far,

axes: [{
            type: 'Time',
            position: 'bottom',
            fields: ['date'],
            dateFormat: ' M ',
            label: {
                rotate: {
                    degrees: 90
                }
            }
        }],