It has been established that current dating techniques using radioactive decay of isotopes can no longer be considered accurate due to their now-confirmed variance in the solar environment,so thus I had mentioned that there isn't really a way to confirm the age of the Moon.
However- to really answer the question of the suspected age of the Moon (according to EU theory), I have heard discussions as to the age of the current arrangement of the inner solar system, but I haven't heard anyone mention any reference as to when the moon might've showed up.
I am not the EU 'Oracle of Delphi' however, so maybe I should've kept my mouth shut and let someone who actually knows that answer... answer!
Sorry about that, Nereid.