Box Plots & Time Series


I have an issue in displaying box-plots where the Y-axis should be a time series result.  My data involves a set of repeated experiments which are used as the x-axis.  I then want to show the population distribution for each experiment round as a box-plot of the time series.  However, SpotFire tells me that this is an invalid argument.

If I take my timeseries column and convert to reals real([TIME]) , it works, but the numerical output isn't easy to digest.

Why doesn't this work when my continuous data is set as a timeseries?