The Date of the Invasion
I once found an article arguing that the date of the invasion was in fact 1898, with examples from the book, but I can no longer find it. Ah well.
In response to your diary comment about Roosevelt's encounter in Global Dispatches, I had always assumed his account came a bit before the invasion proper, and he had discovered a vanguard force. That would explain how he had to head back to the states and rally a force to attack the Martians in Cuba. It's unlikely those Martians survived the tropics of Cuba long enough for him to get a fight out of them, but when the actual invasion hit two years later and he was president, he'd get plenty of fighting.
Unfortunately, because the stories in Global Dispatches are penned by different authors, they don't all agree on details. Despite this, I am generally able to explain away discrepancies where it is needed. (Except Jules Verne's odd account. Usually I just skip that one upon re-reading.)