The way The Stanley Parable knows when to grant the Go Outside achievement is by looking at your last played date as reported by Steam and checking to see if it's at least five years behind the current system clock date. When you reinstall a game you haven't played for a while, it temporarily overrides the last played date to the present, presumably since Steam's default assumption is that you're installing for the first time regardless of any prior playtime.





It should be immediately apparent how this may cause an issue. If you run the game in this state, you will not earn Go Outside, as the game will not see the correct timestamp for when you have last closed it. To fix this, restart Steam by right clicking on its icon in the system tray, exiting the application, and then launching it again; your last played date should automatically revert to its correct value.