I am using matplotlib for a web application to create trend charts from measurements stored in a database.
Specifically I use plot_date to plot the values vs their timestamps.
Occasionally and without any obvious to me reason, plot_date raises the exception
"ordinal must be >= 1"
I check that both the x and y value sequences are not empty and their length is certainly above 1.
Does anybody know where this "ordinal" refers to and what might be causing this error?
Thank you very much