OK, I've passed the glitches with the dates and am on to plotting a time series of data using plot_date. My data are currently represented as a masked array and there are missing values. I vaguely remember seeing something about this while I was reading but I can't for the life of me find it and the search facility on the sourceforge mailing list site is down.
When I plot the data with missing values (say the mask is 1.0e20) it obviously screws up the range of the y limits. I've seen other packages which understand a missing_value attribute or a fill_value attribute and leave that section of the curve blank. I was hoping for a behavior similar to Matlab, when the data vector contains NaNs. I see some mention of this in the matplotlib-devel list (J. Whitaker's patch for pcolor) and I see a keyword argument for contourf that seems to address this situation. Is there anything for line plots?