For Victoria Revolutions, check the forums for the NTL or No Time Limit patch. However, it will not work for a steam copy of Victoria Revolutions...For HoI 2, check its respective fora (I believe it is hard coded). Darkest Hour is soft coded so you just edit a scenario file (.eug file, found in: C:\Darkest Hour A HOI Game\scenarios), changing a start date and end date.