Wrong graph from scatter plot

I created a simple sheet to record my sleeping time and date, as well as waking up time. I tried to plot a graph to see the trend of my sleeping time, together with waking up time on the same graph, and date as x value. I used scatter plot, and set sleeping time and waking up time as two series. The graph given is not what I expecte. It should be two different fluctuating lines with waking up time over sleeping time, instead of two straight super posed lines increasing at the same time. Can anyone tell me what is going on with the plot? Or which plot should I use to plot two differenot time on the same graph and how?

Thanks in advance