Changing the sky texture

Soo... I've recently seen this video called ''the biggest hack ever-unturned'' and it shows that he changed the yukon snowy skies to clear blue skies. Could someone please help and make a tutorial on maybe changing the night sky to day?

i saw that video too. but it doesnt work on multiplayer

- - - Updated - - -

btw how do i post a on this website?

its already been updated no one can do it except for the ones that has ESP...