If by any chance you're running an Ethereum node, and you happen to run Geth (the official node, made by the guys from the Ethereum foundation) then you'd better start thinking about upgrading it. According to a post on reddit, by one of the core developers, the update should start with at least one week before the official date.
October 17th was compiled after the block number, 4,370,000, which is the block from which older clients will cease to work. It was announced previously and re-confirmed on this latest release, that you can find on GitHub.
For the Rinkeby testnet, the hard fork will occur on block number 1,035,301 (~9th October).
I'm a serial entrepreneur, blogger and ultrarunner. You can find me mainly on my blog at Dragos Roua where I write about productivity, business, relationships and running. Here on Steemit you may stay updated by following me 
You can also vote for me as witness here:
https://steemit.com/~witnesses
If you're new to Steemit, you may find these articles relevant (that's also part of my witness activity to support new members of the platform):