Glad someone's mentioned this. Even if we can suspend our disbelief enough that someone as meticulous and obsessive about time and accuracy as Fogg wouldn't have known about the international date line and gaining a day, I've always had a problem with him not realising this during the 2nd half of the journey.
You'd think someone on the crew of the Carnatic (think that's the boat he crossed the Pacific on!) would have mentioned it, especially when there are so many time changes during that voyage. And then we're supposed to accept that he never saw a newspaper or something with "today's date" on during the whole time he crossed America, either at the stations or in the New York shipping office or somewhere (you'd think with the election hoo-har he entered in San Francisco, the date would have been shown at least once).
And even if we do accept all that, like you say, the China would have been due to depart on a set date - that he missed it, the only explanation would be that the China left a day early and no-one bothered to mention that, they only told him that it had already gone.
And then he'd have not seen a newspaper or the date anywhere else back in England.
It makes for one of the greatest twists in English literature - it's so good I wish I didn't already know the story when I read the book - but the suspension of disbelief is just too much.