In the most recent edition of "The Amber Spyglass" released in the UK, the post-script "Lantern Slides" section shows Lyra studying the alethiometer (a rare truth-telling device) with Pantalaimon at age 18. She is excited to start recognising a pattern in the readings, and Pullman tells us that this discovery of a pattern is the "second thing she said to Will next day in the Botanic Garden", implying that the next day was Midsummer's Day, when she and Will would be sitting on the same bench in their separate worlds.