When you save files on a FAT32 drive in Windows 11, the file’s modify time may lose sub-second accuracy. This means the timestamp shows only whole seconds instead of fractions like 10:15:30.123. The issue occurs because the FAT32 file system does not natively support high-precision timestamps, and Windows 11 applies a default rounding behavior that discards milliseconds. This article explains why Windows 11 drops sub-second precision on FAT32 and provides two methods to preserve or restore accurate modify times.
Key Takeaways: Restore Sub-Second Timestamps on FAT32 Drives
- File Explorer > Properties > Previous Versions: Does not help because FAT32 lacks volume shadow copies; sub-second data is lost at write time.
- Command Prompt with fsutil: Query the file’s NTFS-based metadata if the file was originally created on NTFS, but FAT32 stores only whole-second values.
- Convert FAT32 to NTFS using convert.exe: The only permanent fix to preserve sub-second precision on the drive itself.
Why Windows 11 Loses Sub-Second Accuracy on FAT32 File Modify Times
FAT32 is a legacy file system designed in the 1990s. Its on-disk format stores timestamps with a resolution of two seconds for modify time and one second for creation and access times. The file system does not have any field for milliseconds or fractions of a second. When Windows 11 writes a file timestamp to a FAT32 volume, it rounds the value down to the nearest whole second and discards the sub-second component.
The Windows 11 file system driver (fastfat.sys) handles this rounding during the write operation. Even if an application passes a high-precision timestamp through the SetFileTime API, the driver truncates the sub-second portion before storing it on disk. When you read the file’s modify time later, the operating system returns only the whole-second value. This behavior is by design and applies to all FAT32 volumes regardless of the storage medium, including USB flash drives, SD cards, and older external hard drives.
The issue becomes noticeable when you copy files from an NTFS drive to a FAT32 drive. NTFS supports 100-nanosecond timestamp resolution. After copying, the modify time on the FAT32 destination loses its sub-second accuracy. This can cause problems for applications that rely on precise timestamps, such as backup software, version control systems, or media encoding tools that track file changes by the millisecond.
Steps to Preserve Sub-Second Modify Times on FAT32 in Windows 11
Because FAT32 cannot natively store sub-second data, the only reliable fix is to convert the drive to a file system that supports high-precision timestamps. The following methods cover both temporary workarounds and the permanent conversion to NTFS.
Method 1: Convert the FAT32 Drive to NTFS Using the Command Prompt
- Open Command Prompt as Administrator
Press the Windows key, type cmd, right-click Command Prompt in the search results, and select Run as administrator. Click Yes in the User Account Control prompt. - Identify the drive letter of the FAT32 volume
In the Command Prompt window, type wmic logicaldisk where filesystem=”FAT32″ get deviceid, volumename and press Enter. Note the drive letter, such as D: or E:. - Run the convert command
Type convert D: /fs:ntfs and press Enter. Replace D: with the actual drive letter. The conversion process does not delete files on the drive. If the drive has a volume label, you may be prompted to enter it. - Wait for the conversion to complete
The process may take several minutes depending on the drive size and file count. Do not close the Command Prompt window or disconnect the drive during conversion. When done, the message Conversion complete appears. - Verify the new file system
Open File Explorer, right-click the drive, and select Properties. The File system line shows NTFS instead of FAT32.
Method 2: Use a Third-Party Tool to Preserve Timestamps During Copy Operations
If you cannot convert the drive to NTFS, you can use a tool like robocopy with the /COPYALL and /DCOPY:T flags to copy files while preserving NTFS timestamps. However, this does not restore sub-second accuracy on the FAT32 drive itself. It only keeps the original timestamp data in the copy operation’s log. To check the original timestamp, run:
- Open Command Prompt as Administrator
Follow step 1 from Method 1. - Use robocopy to copy files with full timestamp preservation
Type robocopy C:\Source D:\Destination /E /COPYALL /DCOPY:T /R:0 /W:0 and press Enter. Replace C:\Source with the source folder path and D:\Destination with the FAT32 destination path. The /COPYALL flag copies all file information including timestamps, but the FAT32 destination still stores only whole-second values. - Check the robocopy log for original timestamps
Add the /LOG+:copy.log flag to save the operation details to a file. Open the log in Notepad to see the source timestamps with full precision. This does not change the FAT32 storage but provides a reference.
Common Issues and Limitations When Sub-Second Accuracy is Lost on FAT32
Windows File Explorer Does Not Show Milliseconds Even on NTFS
By default, File Explorer displays timestamps to the nearest second. To see sub-second values, you must use a PowerShell command. Open PowerShell, navigate to the file’s folder, and run Get-ChildItem | Format-Table Name, LastWriteTime. The output includes milliseconds for files on NTFS volumes. This command works on FAT32 as well, but the millisecond value always shows .000 because the file system does not store that data.
Copying Files Back to NTFS Does Not Restore Original Sub-Second Timestamps
When you copy a file from FAT32 back to an NTFS drive, Windows 11 uses the FAT32 timestamp as the source. The sub-second data that existed before the first copy is permanently lost. The only way to preserve the original high-precision timestamp is to keep the file on the NTFS source drive and never copy it to FAT32, or to convert the FAT32 drive to NTFS before writing any files.
Some Applications Write Their Own Timestamp Metadata
Certain applications, such as digital cameras and video editors, store the original timestamp in the file’s internal metadata, not in the file system’s modify time. For example, a JPEG photo may contain EXIF data with the capture time including fractions of a second. In this case, the file system timestamp is irrelevant, and you can recover the sub-second accuracy from the metadata using tools like exiftool. This workaround applies only to files that embed their own timestamps.
FAT32 Timestamp Resolution vs NTFS Timestamp Resolution
| Item | FAT32 | NTFS |
|---|---|---|
| Modify time resolution | 2 seconds | 100 nanoseconds |
| Creation time resolution | 1 second | 100 nanoseconds |
| Access time resolution | 1 day | 1 hour (default) |
| Sub-second storage | Not supported | Supported |
| Maximum volume size | 2 TB | 256 TB |
| Maximum file size | 4 GB | 16 EB |
The table shows that FAT32 lacks the ability to store any sub-second data. NTFS provides 100-nanosecond resolution for both modify and creation times. If your workflow depends on millisecond-level accuracy, NTFS is the only native Windows file system that meets this requirement. exFAT, another common file system for removable drives, also supports sub-second timestamps with a resolution of 10 milliseconds, but it is not discussed in this article because the question specifically targets FAT32.
You can now convert any FAT32 drive to NTFS using the convert command or use robocopy logs to track original timestamps. For files that contain embedded metadata, use a metadata extraction tool to recover sub-second accuracy. If you need to maintain high-precision timestamps frequently, consider reformatting new drives as NTFS or exFAT before copying files. This prevents data loss from the start.