The epilogue of Harry Potter and the Deathly Hallows began with three words: “Nineteen years later…” When the book was released that day was still a decade off. Fans did the math, accounting for the amount of time it would take from the Battle of Hogwarts and marked mental calendars accordingly. The years ticked by.

You woke up on an ordinary day and “nineteen years later” was now.

It’s weird when pop culture catches up with you. Reading 1984 after the year 1984 has been possible for three long decades. We all waited with bated breath for October 21st, 2015 hoping that the sunrise would herald a sudden shift, and we’d all wake up in Hill Valley riding hoverboards. It was weird watching the Olympics in 2012 and expecting the Doctor to grab the torch during that last stretch and light the Olympic flame. In another fifteen years we’ll have reached the day that Michael Ironside steps onto a submarine in SeaQuest 2032, and then where will we be?

But today is September 1st, 2017. It’s the day that Harry Potter and Ginny Weasley wrestle three children all the way to King’s Cross Station. The day that Albus Potter gets on the Hogwarts Express after expressing fear to his father that he might get Sorted into Slytherin House. Schools starts on a Friday this year for wizards, which seems nice if they get the weekend to relax after the Sorting ceremony. (It always starts on September 1st, you ever think about that? Like, regardless of the day of the week, so I guess you could end up on the Sunday train to Hogwarts unless wizarding weeks are different somehow.)

There’s something strange about marking out a real world date in a piece of fiction, especially if that date will arrive sometime in the future. Like the recently-passed solar eclipse, it can make one feel as though universes are converging. You pass through a point in time and touch on something that has already “happened” to you, in a sense; studies on mirror neurons have found that when people read about experiences, their brain is stimulated in the same regions that it would be if they had gone through the experience themselves. Reading fiction is no different, and viewing media is relatively similar. Stories, especially beloved ones, feel like events that we have lived through. When a specific date is affixed to those events, we can live them again.

And so we mark our present with stories of the past and stories that will be. 221B Baker Street houses a Sherlock Holmes museum (though there never was such an address in Holmes’s day), complete with a carefully decorated flat. Cardiff Bay’s Mermaid Quay contains a memorial to Torchwood’s Ianto Jones, populated by fans since his “death” in 2009. Riverside, Iowa has a plaque (nonchalantly planted in the backyard of a hair salon) that reads “Future Birthplace of Captain James T. Kirk”, along with the date of Kirk’s birth in 2228. It happened to us, so we remember it, regardless of whether or not it has already taken place.

But now it is September 1st of the year 2017, and one of those events shifts from the future to the past. There is nothing quite so surreal as that. It’s a temperate day in London, with periods of sun and clouds. A good day to get on board a train and travel eight hours to a castle in Scotland. It is the same day we said goodbye to a particular story that defined a generation. But that day hadn’t happened yet, or rather, when it first happened to you it was probably a hot day in July of 2007. You were doing a bit of forward-moving time travel. The next time you experience it, you’ll have to go backward. There are actors performing this day on stage as we speak, stuck in a never-ending loop.

If anything proves that time is an illusion, it must be this.

So hello once more to the end of the Harry Potter series. Goodbye once more, until you need to look back and find it. It will always be there… but it will never happen again.