I'm disappointed that it won't intepret gmt and bst when entered into the search bar, but it clearly knows what they are in the results.

Ergo you can't search;

"hours between 1pm GMT march 10 and 1pm BST march 11 2012" http://www.wolframalpha.com/input/?i=hours+between+1pm+GMT+m...

And get a desired response. In fact it really screws up. Going to keep trying, also I thought that BST kicked in at the end of March. (Google informs me: 25th march)