When was Gandalf in Moria?

[Tuor of Gondolin]

That's an interesting theory about Strider not
going all the way to the West Gate. While it
may seem pedantic, it would square with his
letting Gandalf determine the way through
Moria. If he hadn't been all the way through
he wouldn't have Gandalf's firsthand knowledge.

Also, (somewhat erratically inspired?) foresight
seems to be a not uncommon occurence in even
the Third Age. Witness Eomer's response to
Aragorn:

'Thus we meet again, though all the hosts
of Mordor lay between us,' said Aragorn. Did I not say
so at the Hornburg?'
'So you spoke,' said Eomer, 'but hope oft
deceives, and I knew not then you were a man foresighted.'