October/November and March/April are the months when airline schedules on long distance West - East - West flights are pretty much a work of fiction.
The winds have an annoying habit of refusing to recognise the IATA scheduling seasons so flight times can be out by over an hour in extreme cases. Airlines' operational departments have brought pressure to bear for years to try and get monthly or at least quarterly schedules to ameliorate this but commercial "wisdom" has always prevailed. Gate holds to absorb the time are not permitted at congested airports hence the early arrivals from the US in October.