Is it likely that ALL of these dates are 2015-05-15 00:13:55? And since the the numbers differ, that this is some high-frequency data, and sub-second only would differ?
I think this might be Excel date format, I converted first and last with:
Whatever it is, it would be nice that you could convert from some much used date “formats” (also great if people would actually just use some [ISO] standard, YYYY-DD-MM …). It could be done with a package, but these are simple calculations, from Unix timestamp (I believe already supported), and some others, the code would be similar, just different scaling and offset.
I’ve had do do similar calculation when porting from Matlab, I don’t recall if some internal Matlab format was used, or if it just came from Excel. I THINK that Python uses Unix timestamp internally, also on Windows, but that would then never be a float.