The Percy Jackson series just hit 500 weeks on The New York Times Bestseller list

Author Rick Riordan hit a huge milestone this week.

The Percy Jackson and the Olympians series hit its 500th week on the New York Times Bestseller list for Children’s Series Books. If our math is correct, that’s just over nine and a half years!

Hannah Allaman, an assistant editor at Disney Hyperion (Riordan’s publisher), took to Twitter to celebrate.

Percy has been hanging out on the NYT bestseller list for 500 WEEKS!! We’re celebrating in the Disney office with cake and @camphalfblood! 😂🎉 pic.twitter.com/EX4V6JJMyb

— Hannah (Allaman) Hill (@hannahhill1225) April 17, 2019

“We’re celebrating in the Disney office with cake and (Rick Riordan),” she tweeted, with a photo of the cake and a printed picture of Riordan.

The Percy Jackson series was 10th on the bestseller list. It’s not the only series enjoying longevity on the list either. Jeff Kinney’s Diary of a Wimpy Kid books were second in the rankings — those books have been on the list for 526 weeks. And J.K. Rowling’s Harry Potter series took the third spot, with 525 weeks to boast.

The first Percy Jackson book, The Lightning Thief, hit shelves in 2005. Since then, Riordan’s completed the series, written a sequel series, written a couple of spin-off series and launched a publishing brand that gives voice to diverse authors. (Also, a couple of terrible movies came out but we don’t talk about those.)

Related: ‘The Lightning Thief: The Percy Jackson Musical’ is the adaptation fans deserve

What’s next for Riordan? His imprint, Rick Riordan Presents, will publish three books from diverse authors later this year. Those include The Fire Keeper by J.C. Cervantes, Tristan Strong Punches a Hole in the Sky by Kwame Mbalia and Race to the Sun by Rebecca Roanhorse.