Cannot plot Quantity values with DateListPlot

Question

Bug introduced in 9.0.0 and fixed in 9.0.1

Quantity is new in 9.0.0

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Is there a way to use DateListPlot with Quantity values? I retrieved the following time series data from WolframAlpha:

gasPrices = WolframAlpha[
"us gas prices", {{"History:Price:GasPriceData", 1}, 
"TimeSeriesData"}];

Each data point is composed of a date and a Quantity:

{{{1993, 4, 5, 0, 0, 0.}, Quantity[1.068, ("USDollars")/("Gallons")]},
 {{1993, 4, 19, 0, 0, 0.}, Quantity[1.079, ("USDollars")/("Gallons")]},
...
 {{2012, 12, 31, 0, 0, 0.}, Quantity[3.369, ("USDollars")/("Gallons")]} }

I can plot the values using ListPlot:

 ListPlot[gasPrices[[All,2]]]

Strangely however, DateListPlot produces an empty plot:

 DateListPlot[gasPrices]

To get DateListPlot to produce a proper plot I have to do this instead:

DateListPlot[ Transpose[{gasPrices[[All, 1]], gasPrices[[All, 2, 1]]}] ]

Am I missing something? I would have thought that Quantity values could be taken directly by DateListPlot, as they are by ListPlot.

Answer 1

This appears to work in the 9.0.1 release:

 DateListPlot[gasPrices]