How is the Zakat calculated for two sums of money, knowing that the first sum has had a full year pass over it, and the second was added a short while later?

If the money that has completed a full lunar year reaches the nisab (definition) (minimum threshold), then its zakat (definition) is obligatory, at a rate of one-quarter of one-tenth (2.5%). This can be paid from the money itself or from other newly acquired funds. As for money acquired during the year, the majority of scholars hold that its zakat is not obligatory until a full lunar year has passed since it came into the owner's possession. However, the Hanafis believe that its zakat becomes obligatory along with the principal money, which is easier for the zakat payer and more beneficial for the poor.