FileAge returns a time stamp used by the OS to record information such as the date and time a file was modified.
You should use the FileDateToDateTime function to convert the Integer value to a more manageable TDateTime format:
FileDateToDateTime(FileAge(fileName));
Note:
function FileAge(const FileName: string): Integer; overload;
is deprecated. There is another version of FileAge
function FileAge(const FileName: string; out FileDateTime: TDateTime; FollowLink: Boolean = True): Boolean;
that returns the time stamp of FileName in the FileDateTime output parameter.
FileAge(filename, timeDate);
EDIT
Depending on the use of the data, it may be (very) important to convert from UTC to local time.