Palitana’s Shatrunjay Tirth does not have one fixed age, because it is a sacred hill and temple complex, not a single building. In Jain tradition, Shatrunjaya is considered ancient and sacred since the time of Lord Rishabhanatha (Adinath), the first Tirthankar. ( jainheritagecentres.com)

If you mean the present temples, many of them are medieval and later, and some are over 900 years old; the complex has been built and renovated over roughly a thousand years. ( lonelyplanet.com)

So, in simple words: Shatrunjay is traditionally believed to be extremely ancient, while the current temple structures are mostly about 900–1000+ years old. ( jainheritagecentres.com)