When Does "John Wick: Hex" (2019) Take Place?
"John Wick: Hex" is a crime video game written by Mike Bithell, designed for personal computers running Mac or Windows, that released October 8th, 2019. So when is "Hex" set?
It takes place on the fictional John Wick timeline roughly in the year:
We know this because at the beginning of the game John Wick is a professional assassin as he has become by the end of the comic-book mini-series "John Wick" #1-#5 (2017), which takes place sometime during or after 2005 AD. So it must be during or after 2005 AD.

late 2000s AD
We know this because at the beginning of the game John Wick is a professional assassin as he has become by the end of the comic-book mini-series "John Wick" #1-#5 (2017), which takes place sometime during or after 2005 AD. So it must be during or after 2005 AD.
Also, there is no discussion about a return from a retirement for Wick as seen in the feature film "John Wick" (2014), which takes place in autumn of 2014 AD. So it is probably before autumn of 2014 AD.
More specifically, the very first frame of the game is a white-on-black title card reading "Some time ago... before Helen.", referring to John's wife, Helen Wick, who dies shortly before the main action of "John Wick" (2014), which takes place in 2014 AD. At the beginning the last stage of the game, Hex says, "Thank your god that won’t live to lose what you’ve taken from me." While Hex can’t know John’s personal life, John does not react to this emotional line about a lost loved one, again strongly implying we are "before Helen."
Now, during the first film at the Continental hotel Addy asks, "How long has it been? 4 years?" to which John Wick replies, "5 and change." strongly implying over 5 years have passed since Wick would have last visited before his retirement, which happened after he met Helen. So this video game is most likely during or before 2009 AD.
2014 - 5 = 2009.
After some time in 2005 AD but before some time in 2009 AD means this could be: 2005 AD, 2006 AD, 2007 AD, 2008 AD, or 2009 AD.
It is the chronologically third-earliest story in the John Wick universe (the first chronological game to feature John Wick) and can be played at its timeline point, as en extended flashback after "John Wick: Chapter 3 - Parabellum" (2019), or entirely separately.

