If I were to travel on the 30th day of Ramadaan from London just after Magrib time, after having broken my fast and I were to arrive at my destination in the USA but to find that they are still in the day time of their 30th day of Ramadaan, what should I do?
The reply to your question in brief is: your state should be similar to that of the [Muslim] inhabitants of where you are. So, if they were still observing fasting then you should observe fasting with them even if that means you would be fasting for more than 30 days [the max. number of days, normally observed in the month of Ramadaan]. This is the opinion of Shaikh Abdul-Azeez Ibn Baaz.