Dont Blame American Airlines, Blame George W Bush he changed USA and subsequently the rest of North America and made the dates totally different dates to the Reminder of the World that undertake Saving time changes.

https://newrepublic.com/article/7902...ht-saving-time

Whilst not too awkward for most places, for Heavily congested Airports like London Heathrow they have to cope with 3 different arrival times changes and slot congestion in the same month twice a year,