The start and end dates for Steam’s upcoming Halloween, Winter, and Black Friday sales were leaked on Reddit earlier today. Despite being taken down for being unverified, sources at Eurogamer have since “independently corroborated the dates as correct”.

Assuming the leak is true, the dates for Steam’s reamining 2017 sales are as follows:
- Steam Halloween Sale: October 26th - November 1st
- Steam Black Friday Sale: November 22nd - November 28th
- Steam Winter Sale: December 21st December - January 4th 2018
Despite the apparent corroboration, these dates have yet to be confirmed by Valve and are thus still technically rumors.
Steam sales have changed quite a bit over the past couple years, with the removal of flash and last chance deals among the notable changes. As such, we can assume that the pricing for the sales above will last through the full duration of those sales. We will keep you apprised of the details if any new information is announced regarding Steam’s remaining sales of 2017.