With the windowing method, only programs are altered, while data files are left untouched. This method will only work, however, within a range of 100 years. Furthermore, in a large system, different applications might require different dates as the baseline, and as time goes by it could be necessary to shift baselines forward or backward.
「區間法」只修改程式而不必修改資料檔，然而它的業務涵蓋範圍只有一百年；而且在一套大型的應用系統裡，可能不同的程式會需要不同的基準年。