Is zakat obligatory on money saved in the bank from the date of its deposit, or from the date of the last withdrawal and redeposit of the money?

Regarding zakat, it begins when the money reaches the nisab. The hawl (one lunar year) is not affected by withdrawals unless the money falls below the nisab. In that case, the hawl is interrupted and there is no zakat. If the nisab is met again, the hawl begins anew, because the completeness of the nisab throughout the entire hawl is a condition for the obligation of zakat, according to the majority of scholars.