US v UK DST can cause problems. The date thereof differs.

I was working for a UK flight instrumentation company that was taken over by GE at the time. The e-mail system was then locked-in to a central app/server in Cincinnati A meeting was called by e-mail, word of mouth, phone and probably spirit guides, just between the DST changes. About an hour before (or at the appointed time in my case) it was called off, because some people had used the calendar in the e-mail system, some had just told contract workers like me.

And you can guess the result. No-one in the US was involved! Computers are clever, people - er - notso!

My Canadian cousin told of DST & Double DST for farmers and there were towns that didn't (in the 50's). He was a travelling salesman, so imagine the confusion there.