J.K. Rowling just revealed a detail about the 'Harry Potter' series readers have always puzzled over

At the close of J.K. Rowling's "Harry Potter" series, there is an epilogue where Harry and his wizarding pals are all grown up and dropping off their children to board the Hogwarts Express. The scene takes place at an undisclosed date, 19 years after the Battle of Howarts. 

Or so we thought.

Earlier today, Rowling asked her Twitter followers in London to wish James S. Potter, son of Harry Potter and Ginny Weasley, good luck on his first day at Hogwarts. 

 Here's Rowling's tweet. 

In the epilogue, Harry Potter is dropping off his two sons, Albus and James, at King's Cross station to board the Hogwarts Express. James has already been a Hogwarts student for two years at this point and it's Albus' first year.

Using Rowling's tweet as a time-stamp, if September 2015 marks James' first day at Hogwarts, than means the epilogue in "Harry Potter and the Deathly Hallows" takes place two years later, in September 2017. 

Twitter users immediately picked up on the detail. 

 The hashtag #BacktoHogwarts also began trending on Twitter. 

Though for some, James Potter's first day at Hogwarts was just a reminder that they were still stuck in the muggle world. 

Join the conversation about this story »

NOW WATCH: This guy combined photos of celebrities to create portraits of flawless superhumans