Is it permissible to pay Zakat on money from other money upon which a year has not passed?

Whoever is obligated to pay Zakat on wealth should disburse it, whether he takes it from the very wealth subject to Zakat, or from another wealth not subject to Zakat. For instance, if someone has the minimum Zakat-eligible amount (nisab) in an account and a year has passed over it, there is no difference whether he pays its Zakat from that account or from a salary he received at the same time.