The amount of time that firewood needs to season or cure varies on the species of wood.
Oak firewood needs at least 2 years to fully season and dry out enough to where it will burn in your wood stove.
Other species of wood can usually be burned within 6 months after cutting the tree and splitting the firewood.
Of course it's best to let the firewood season for at least 1 year if possible because it will dry out better and provide more heat output as well as ignite in the wood stove much better.