Well that's dateutil (installed from pip) and not datetime (std). As part of log ingestion I would, of course, convert to UTC and drop the timezone distinctions

Well that's dateutil (installed from pip) and not datetime (std). As part of log ingestion I would, of course, convert to UTC and drop the timezone distinctions since it does slow down python a lot when it has to worry about timezones. Working within the same units and no DST issues is much nicer/quicker. Anyway, if you're installing packages from pip, may as well just install iso8601 and get the best performance - possibly beating .Net (who knows? as you said, I have a different machine than OP).