Thursday is Back to Hogwarts Day. The Sept. 1 anniversary marks the day where characters in the Harry Potter universe return for their first day of classes at Hogwarts School of Witchcraft and Wizardry. While the main characters may have grown up and moved on, fans everywhere still rejoice and reflect on the days when Mr. Potter, Ron Weasley and Hermione Granger walked the halls of the legendary institution.

JK Rowling, the creator of the Harry Potter series, paid tribute to the special day by tweeting to fans, Hello! reported. She tweeted, "If you're at King's Cross, the Potter, Granger-Weasley and Malfoy families are there too. Albus Severus starts school today. #19YearsLater." The author later corrected herself upon realizing that those 19 years she was referring to were actually a reflection of her successful play, “Harry Potter and the Cursed Child,” which takes place 19 years after the Harry Potter book series.

Fans on Twitter were reminiscing about the day when students and parents gather on platform nine and three-quarters at Kings Cross Station in London, saying their goodbyes as the children board the train destined to arrive at the school run by Headmaster Albus Percival Wulfric Brian Dumbledore.

Upon arrival to the school, students are treated to a large feast in the great hall where the ceiling is typically manipulated by magic and projects an image depending on the occasion of the event. In the middle of the speech, the headmaster addresses the students and makes announcements pertaining to new staff, upcoming events in the school year and warnings depending on the state of things in the wizarding world.

Students are housed in one of four dormitories on the school grounds. Gryffindor, Hufflepuff, Ravenclaw and Slytherin are the houses named after the wizards and witches that founded them. Each house possesses a coat of arms and house ghost that roams the common room and school grounds.

The first book of the series, “Harry Potter and the Sorcerer’s Stone,” originally known as “Harry Potter and the Philosopher's Stone” was published in 1997. Several books followed as well as a billion-dollar movie franchise. Millions of fans continue to remember the little moments that made the series special.

Check out the tweets from Harry Potter fans celebrating Back to Hogwarts below.