How can a young man determine the due date for paying the zakat on his savings in the bank, knowing that he is accustomed to paying it in Ramadan, that he sometimes withdraws from it, and that he cannot accurately determine the beginning of the hawl (zakat year)?

Whoever does not know when their wealth reached the nisab (minimum taxable amount) should investigate and act according to what they most likely believe will clear their conscience. They should designate the time they most likely believe the nisab was reached as the time for paying zakat. By doing so, their conscience will be cleared, as Allah Almighty says: "So fear Allah as much as you are able." (Quran 64:16). Wealth acquired during the year has a detailed ruling, and what is spent from it is not subject to zakat. Paying zakat in Ramadan suffices for what has been paid. However, if Ramadan comes after the zakat due date, according to what is most likely believed, then one is sinful for delaying zakat. But if it comes before, there is no harm, as hastening zakat is permissible according to the majority of scholars.