In Marvel Universe it just states that he was born into one of the leading Kree aristocratic families on Hala, but nothing on how old or when he was born?
Is he in the hundreds of years or still very young?
Been looking for this information for the past 2 days.
Ronan (Earth-616)'s first appereance was in Fantastic Four Vol 1 (Issue #65) which was published in August, 1967. It's the birthday of the character in our universe.
However, it seems OP is asking in universe date of birth, which is unclear. In Marvel Wikia, earliest entry about Ronan's life is as follows:
Upon the completion of his formal education, Ronan was enrolled in the Kree Public Accuser Corps, the main law enforcement body for the empire. Ronan did well and was steadily promoted. In a border incident, he stopped a fleet of Skrull ships from entering Kree space. As a result, he was made Supreme Accuser of the Kree Empire, making him responsible for enforcing the laws and decrees of the Kree, and second only to the Supreme Intelligence, and the Imperial Minister. As a proud member of the Kree aristocracy (blue-skinned Kree), he was not happy taking orders from the Supreme Intelligence. His attempt to cause a civil war was quickly halted, and he quickly returned to service.
And about his origins:
Born to Kree aristocracy, Ronan became Supreme Accuser (leader of the Kree Public Accusers) after distinguishing himself as a governor of worlds.
Hala, Pama System, Kree Empire in the Large Magellanic Cloud.
Here is a picture of
potato LMC and SMC over Paranal Observatory (Cerro Paranal, Chile) for better judgement:
The very first recorded mention of the Large Magellanic Cloud was by the Persian astronomer `Abd al-Rahman al-Sufi Shirazi, in his Book of Fixed Stars around 964 AD.
First appreance of Planet Hala was in Captain Marvel Issue #1 which was published in May, 1968. During an attack by Mister Knife and his Slaughter Lords, Hala was destroyed (Guardians of the Galaxy Vol 3 Issue #25, published in May, 2015).