As Valve has yet to officially confirm or deny any of the leaks, fans are urged to take the information with a grain of salt for now. However, the dates in question do line up with sale events that have run in the past few years, adding a bit more credibility to the reports. Until official word, then, the potential Steam sale event start and end dates are as follows:

Halloween Sale: October 26 to November 1. Black Friday Sale: November 22 to November 28 Annual Winter Sale: December 21 to January 4, 2018

The leaked information initially appeared on Reddit, but the post was removed due to a lack of a source. Interestingly enough, Eurogamer picked up the slack soon after and managed to independently corroborate the information and dates in the original Reddit post. In keeping with tradition, Flash and Last Chance sales won’t be returning, so fans don’t have to worry about the already deep sales prices changing at some point during the event.

The removal of Flash Sales at the time was a controversial choice, as many gamers ultimately were not happy with the decision. One of the biggest reasons for the removal however was the addition of an official Steam return policy, which gave fans a way to return a digital game and get their money back if certain conditions were met. Having to potentially deal with a lot fans requesting refunds on a game once it dropped even lower in price was likely a motivating factor to remove the feature.

Source: Reddit; Eurogamer