If it happens after the first block to be mined, then it could be in a day or two.
Indeed it could.
BitcoinABC nodes are 2 blocks behind right now (478558 is the last common block, BTC nodes are at 478560 right now).
According to the fork monitor the split has happened now.
You need a block or a few blocks for a split.
Else you're just running nodes on an outdated version of the chain.