When he gets to Geneva, he grabs the little boy, thinking that he can use the boy to learns where around. But, when the boy mention his fathers name Frankenstein. The monster kill him to get revengen on Frankenstein.
The monster might know thats there is name consistency in the story there that he have read. Because, Victor made the creatures on november.
Then got sick all winter.
William (Victor Frankenstein little brother) got killed the following spring in 6 month later.
But, the creatures spent whole year at the cottage.
And he kills William more like 18 month after being created. So there's different of the year between the two stories.