Sadie and I discovered that the old routine histogram2d was ignoring units when binning by time bins, where the xtags and the range for the bins was assumed to be in the same units. I also found the putValues assumed that NaN could always be used for fill, even when the data was backed by integers and a fill value of 99999 was declared. Both of these come from a time when I was still figuring out how QDataSet would be used.
A review of all codes should be done.
See https://github.com/autoplot/dev/tree/master/bugs/2026/20260223