"I ought to have been specially careful on a Friday," she used to say afterwards..."
See in text (Chapter 2 - The Shadow)
Here Barrie changes the timeline of the story without specifically saying that they have jumped forward without explanation. By using the word “afterwards” at the end of the sentence it is implied that something has happened that readers are unaware of. Barrier does this to add to the suspense of the story and the oral narration tone.
"for it was afterwards to save her life..."
See in text (Chapter 3 - Come Away, Come Away!)
This foreshadows a later event that builds suspense in the story by alerting the reader that Wendy will experience a life-threatening incident. Notice that the button that later saves Wendy’s life came from Peter, so in a way Peter is the one who saves Wendy’s life.
"it had not been ticking..."
See in text (Chapter 15 - Hook or Me This Time)
It is difficult to surmise what this exactly means. One idea is that it foreshadows the end of time for one of the story’s major characters. Another assumption could be that this represents the coming showdown between Peter and Hook.