Zakat of any wealth is given after one year passes over it. But there happens properties for which we give zakat before one year, since we give zakat every Ramadan. Are they counted as sadaqah in this case? If they are regarded as sadaqah, should we give zakat again after one year is due?
In religion, a year is not calculated according to Gregorian calendar, but lunar calendar. Therefore, exactly one year becomes due from one Ramadan to the next one. There is no problem from this point of view and you do not have to give zakat again.