How is Zakat on money calculated if a loan was deducted from the Hijri salary, and it is repaid from the salary of the brother who receives it in Gregorian?

There is no zakat (definition) on the monthly salary as soon as it is received, according to the saying of Ibn Umar (may Allah be pleased with him): "Whoever acquires wealth, there is no zakat on it until a year passes over it." Zakat is only obligatory on previous salaries that have reached the nisab (definition) and a year has passed over them. As for the salary received at the time of zakat payment, a year has not yet passed over it.