Rereading Prince Caspian today, an inconsistency jumped out at me that never did before. It's from the Sorcery and Sudden Vengeance scene. 

"You know well enough," said a voice ("That's the King," whispered
Trumpkin), "why the Horn was not blown at sunrise this morning.
Have you forgotten that Miraz fell upon us almost before Trumpkin
had gone, and we were fighting for our lives for the space of three
hours and more? I blew it when first I had a breathing space."

By my count, three nights have passed since the day Caspian blew the horn. (Trumpkin mentions hearing it from faraway and wondering why it wasn't blown sooner, setting up this surprise attack that delayed it.) Did C. S. Lewis just forget how much time had passed since the ancient kings and queen were called back to Narnia? Or is there a typo in my copy of the book?