If you don't want to wait for the achievement,
And your PC is modern That you can't change the year and date then there is 1 easy way.
You can do that with Steam Deck if you have one

Here's the steps

1 (Turn on deck
2 (Stanley parable ultra deluxe
3 (Turn off Wi-FI
4 (Shutdown game and systeem
5 (Turn on system and go to Bios settings
6 (change the date from 10+
7 (Save settings and turn on systeem
8 (Start stanley parable ultra deluxe
9 (Play a litte bit '''Just walk a bit''
10 (Turn on Wi-fi on the deck


Once it is connected you will be notified that you have achievement
This can also work with the desktop but unfortunately Modern Motherboard (mine aswel not able to do it enymore
So you cann do it with old computer

instead with Wi-Fi you do with internet cable take out (Desktop)