When exactly will the hard fork happen? Is there a definite date for this? Or is this date uncertain? As far as I can see, there are two dates that are not sure around.
Just stick to the date on the site
http://btcgpu.org. It is expected to fork at block 491407 which is estimated to take place in about 23 hours from the time I posted this. It may be a bit longer, or a bit shorter, I guess but obviously within that range. However, the best is just to keep your fingers forked and when it gets forked, you will eventually know.