“I recently worked on a story that had two Mondays in the same week. When I pointed this out, the author was so embarrassed to have made such an obvious error, but it’s a simple mistake to make. Raymond Chandler apparently forgot to reveal who killed the chauffeur in The Big Sleep, and one character in The Iliad was still around to witness his son’s death even though Menelaos had killed him much earlier.
It’s those minor characters that are usually the problem. The little details. You know your main characters perfectly, you can see them in your mind’s eye. But was her mother born before the war or just after? Did he meet his first wife when he was a freshman or was he already a sophomore?
Editors have a similar problem when they start to work on your book. They don’t know anything about your characters, the world they live in, who did what or when, but they still have to keep track of it all. They have to be able to point out that John, who had a bad limp in chapter 3, is now escaping over back-yard fences like an Olympic hurdler or remind you that the witness spoke with a heavy British accent when she was first interviewed but sounds more like a Southern belle when the inspector revisits her later in the book.
Keeping track of all of these details and idiosyncrasies is essential for the editor, and it’s useful for authors too to make sure your characters, settings, style, and backstories are consistent.
Having two Mondays in the same week and other issues with your story’s timeline in particular can be time-consuming errors to correct. It can mean that everything after that blip gets knocked out of sync too. And a simple find-and-replace to change every Monday to Tuesday won’t work as you then have to change every Tuesday to Wednesday and so on, plus check for every mention of ‘yesterday’ and ‘tomorrow’ and ‘day before’ too.
More importantly, a disturbed timeline can confuse readers: ‘I thought the murder happened on Monday, but now she’s saying today is Monday.’ It’s enough to make them drop your book to pick up another. Or worse, leave a scathing review.
It’s especially important to be on top of the timeline in stories if your story doesn’t run in a strict chronological order or you have several or alternating plot lines. Fortunately, there are lots of ways to easily keep track of your novel’s timeline.”