DateTimeZone.FromFileTime(fileTime as nullable number) as nullable datetimezone
Creates a datetimezone value from the fileTime value and converts it to the local time zone. The filetime is a Windows file time value that represents the number of 100-nanosecond intervals that have elapsed since 12:00 midnight, January 1, 1601 A.D. (C.E.) Coordinated Universal Time (UTC).