Is it permissible to calculate Zakat on 31/12 of each Gregorian year at a rate of 2.575% for its ease, and must the amount of Zakat paid in advance be added to the balance at the end of the year before calculating Zakat, and does the supplication: "O Allah, subject to me the earth and all upon it, and the heavens and all within them, and subject to me the people around me and those to whom I have entrusted my affairs, and grant me the most beautiful portions of this world and the Hereafter" contain any Sharia violations?

Scholars have stipulated that for zakat to be obligatory, the wealth must reach the nisab (minimum threshold) and a full lunar year (hawl) must have passed according to the Hijri calendar. This is the more cautious approach. However, it is permissible to calculate it using the Gregorian calendar at a rate of 2.575% if calculation by the Hijri calendar is difficult, and past calculations will be considered correct if this method was adopted.

As for paying zakat in installments before the completion of the hawl, it is permissible if the reason for its obligation (ownership of the nisab) exists. The advance payments are then added to the existing balance when zakat becomes due. If the installments are less than what is obligatory, the remainder must be paid. If they are more, the excess is considered sadaqa (voluntary charity).

Regarding savings, if the accrued wealth is a result of the original wealth, then all of it is subject to zakat upon the hawl of the original wealth. However, if it is not a result of it, then it is permissible to combine the accrued wealth with the original wealth and assign a single hawl for both, or to assign a separate hawl for each.