When you do the Quest in which the merchant has to translate the schemes for you, you are told to wait a day for him to finish.
If you go to the runesmith next to him and pay him money for advancing his shop ( runesmith quest ) you get the message "..a few days later..." ( until his workshop is upgraded).

Now you go back to the merchant cause "a few days have passed" and well he is not ready yet.
The game is still on the same day :D