When you copy a file from a Windows NT file system (NTFS) drive to a file allocation table (FAT) drive, the time stamp changes to an even number of seconds.

File time stamps on FAT drives are rounded to the nearest two seconds (even number) when the file is written to the drive. The file time stamps on NTFS drives are rounded to the nearest 100 nanoseconds when the file is written to the drive. Consequently, file time stamps on FAT drives always end with an even number of seconds, while file time stamps on NTFS drives can end with either even or odd number of seconds.

When files are copied from NTFS drives to FAT drives, some file time stamp rounding has to occur; the file time stamp is rounded up to the next even second.

To preserve exact NTFS file times, always copy files from NTFS drives to other NTFS drives. If you are writing a program to compare file times between NTFS and FAT drives, accommodate for the expected rounding.

For example, when you compare time stamps between an original file in NTFS and a file in FAT, which is copied from NTFS, you will see the following:

NTFS time stamp: 7 hours 31 min 0 sec 000.
FAT time stamp becomes 7 hours 31 min 0 sec 000.

NTFS time stamp: 7 hours 31 min 0 sec 001.
FAT time stamp becomes 7 hours 31 min 2 sec 000.

NTFS time stamp: 7 hours 31 min 1 sec 000.
FAT time stamp becomes 7 hours 31 min 2 sec 000.

NTFS time stamp: 7 hours 31 min 1 sec 999.
FAT time stamp becomes 7 hours 31 min 2 sec 000.