Though there's no problem if your program is only for Windows, you don't need to use the Windows unit. As Handoko said, there are equivalent cross-platform functions in SysUtils (DatetimeToFileDate and viceversa, DateTimeToSystemTime and viceversa, FileAge, FileSetDate, etc.) and other units which would allow you to move your program to, say, Linux or MacOS without having to touch your code (at least in this respect).