How is Zakat paid on savings added at different times of the year?

What is considered for determining the zakat year (hawl) is the Hijri year, not the Gregorian year. The beginning of the hawl is calculated from the date of possessing the amount if it reaches the nisab (threshold). If it does not reach the nisab, then it is calculated from the date it reaches the nisab with what follows it.

The nisab for banknotes is equivalent to 85 grams of gold or 595 grams of silver. If a year passes over money that has reached the nisab, its zakat is paid at a rate of one-quarter of a tenth (2.5%).

Regarding newly acquired money: 1. If it is a result of the initial capital (e.g., profit): It is zakat-eligible with the initial capital, and its hawl is considered the same as the initial capital's hawl. 2. If it is not a result of the initial capital: It can be added to the initial capital, and all of it is zakat-eligible when the hawl of the initial capital is completed. Alternatively, a new hawl can be started for each amount separately, even if it is below the nisab, because it is considered part of the nisab due to the initial capital.

It is stated in "Al-Mughni" by Ibn Qudamah: "If one possesses a nisab, the newly acquired wealth is not devoid of three categories: First: That the acquired wealth is from its growth, like the profit from trading capital or the offspring of livestock. This must be added to what one already possesses of its origin, and its hawl is considered to be the same as its origin's hawl... The third category: That one acquires wealth of the same type as a nisab one possesses, upon which the hawl of zakat has already commenced due to an independent cause... For this, zakat is not obligatory until a year has also passed over it."