Yes is the short answer. All events begin and end simultaneously wherever you are in the world. Everyone gets new levels and episode promotions at exactly the same time (barring local server and ISP issues, of course).

So if Whacking Day ends at, say, noon on May 9 in Los Angeles, it will be:

2 pm in Chicago
3 pm in New York
8 pm in London
9 pm in Paris
11 pm in Moscow
3 am on May 10 in Singapore
4 am on May 10 in Tokyo (where I am this week)
5 am on May 10 in Sydney
7 am on May 10 in Auckland

…but all exactly the same time (I hope I got all that right!).

Now, I’m not saying that’s the time it will end and the final snake could be earlier or it could be later. But EA haven’t announced an extension, so we still need still need to expect the end to come sometime in the next 9 hours or so. But if it does end early afternoon in the US and there’s an update, be patient – because it could all be happening while I’m in bed trying not to dream of snakes and snake eggs.