How old is Gandalf?

As gandalf said in the lord of the rings, "Many are my names in many countries, Mithrandir among the elves, Tharkun to the dwarves; olorin i was in my youth in the west that is forgotten, in the south incanus, in the north gandalf; to the east i go not." olorin is elvish of the elves in the blessed realm. and the essay on the istari (in unfinished tales) tells that the wizards were to be peers of sauron. We know that Sauron was a maiar of aule in the begging but corrupted by melkor so Gandalf was older than the world since he descinded into it with the Valar in the beggining.