In FB post and on Twitter it says this!
"Only a few hours before Spintires: MudRunner's release! (Find the release time in your region here)"
So it must be Steam related mistake!
Spintires: MudRunner releases on Steam at midnight CET (in approximately 3h20).
It was a display issue on the Steam page, it's now fixed.
At this point is still says 20 hours.