While profiling I noticed the same thing about dateutil.parser.parse a few years ago. We standardized all our interacting systems on UTC so we have a regex that

While profiling I noticed the same thing about dateutil.parser.parse a few years ago. We standardized all our interacting systems on UTC so we have a regex that matches UTC and if that fails to match we call dateutil. That way the vast majority of cases are optimized but we still support other timezones.