I've analysed what we do and what they do, and I believe our way is better.  The comparison is essentially the same, although to my mind ours reads a lot cleaner, and the one thing we do different is to search the common timezones first, which will result in quicker matches about 95% of the time.  I think we can justify moving to our comparison as they're computationally the same, but the list comprehensions used by us will be faster than the loops used by them.