But it's taken until August for both sides to finally get around the table and agree a date, with both fighters now having signed contracts for the second bout.
At a press conference in London to officially announce the details had been finalised, Hearn said: "I read several reports yesterday, both fighters have signed for this rematch fight.
“Both fighters have signed for the rematch and all governing bodies have confirmed the dates for this.”
The pair will go toe-to-toe on Saturday December 7, 2019.
As yet, a start time for the contest has not been set.
How to watch and live stream Anthony Joshua v Andy Ruiz Jr in the UK
The fight will be Ruiz Jr vs Joshua 2 live on Sky Sports Box Office in the UK.Fans can purchase the fight for a one-off £19.95 fee.
You can soak up the entire build-up and full undercard ahead of Joshua’s showdown, with several big names expected to be confirmed on the card.
watch AJ vs Ruiz 2 online Box Office customers can also access full replays and highlights the next day.
