For anyone out there:

24 real world hours over multiple Tuesdays

The Commitment achievement in The Stanley Parable requires players to play the game for 24 real world hours over multiple Tuesdays. You can choose to do it all in one Tuesday or break it up over multiple weeks. The 24 hours is cumulative, meaning that you can do it on multiple Tuesdays. To unlock the achievement, you must run The Stanley Parable for the entire 24-hour period of any Tuesday. The achievement uses the computer or console’s clock to determine when it’s Tuesday.

You could leave it running all day which a lot of people do but you can also play different Tuesdays, over time it will count towards it. Changing the clocks do not work, it's been done by a lot of people, it doesnt work lol.

I suggest running it while doing chores, work or watching a show/movie. I believe you can minimize the window as well and it still counts. I would also suggest leaving the game running while in the game not the menu just to be sure (you never know when it comes to valve games sometimes).