DST Compensation doesn't work in File Synchronizatioin

For years I've noticed when DST changes, the next time I do a synchronization between a hard drive folder (NTFS) & thumb drive folder (FAT32), some identical files are flagged as newer. It could be numerous files in a folder, or only a handful. Checking/unchecking "DST Compensation" & "Ignore Seconds When Comparing" may only make a slight difference (e.g., 17 files vs 18 files showing as different). Rebooting and/or removing/replacing the thumb drive after DST changes makes no difference.

It's a major in convenience twice a year that I've lived with in all versions for 15 years now. I could only find one post that directly mentioned it, but it didn't appear to offer a resolution. It's frustrating enough that file synchronization breaks down twice a year, but it's utterly baffling that it happens for some files but not others.

Any suggestions?

Please post a screenshot which shows:

  • How the Sync panel is configured
  • The NTFS and FAT32 files that should be considered identical but aren't, including names, dates and sizes.

The left is a sample folder on the NTFS HDD; the right is the analogous sample folder on the FAT32 thumbdrive. All 23 files are identical, & synchronization before the DST change would say that (though now, after the recent DST change, you'll note 4 are an hour different).

After DST change, the 4 files that are an hour off don't believe they're identical. The ones on the HDD advanced the timestamp an hour, while the ones on the thumbdrive didn't.

"Ignore seconds" & "DST Compensation" are checked.

Here are the properties of the first document on the left & right:

More precisely, the HDD file is dated 59 minutes, 59 seconds later than the thumbdrive file. Sampling numerous examples, I have seen that the difference appears to always be 59 minutes, 59 seconds, or 59 minutes, 58 seconds.

I have seen this handful of differences in virtually every folder I compare, every time daylight savings time changes, for years; I've used Directory Opus for some 15 years. It does NOT occur if I compare to a USB HDD formatted as NTFS.

As I said before, it's a major in convenience, but from a curiosity standpoint, it's hard to understand why most files understand that they're identical, something like 3-10% of the files in a folder get tripped up by the DST change.

I would think the real question is not why sync is behaving the way it is, but why the specific files have different timestamps.

Were the files copied from one of the disks to the other? All of them or just the ones with varying time stamps? Before or after the DST change?

Does File Explorer show the same timestamps?

NTFS and FAT32 have completely different ways to store time.

(For Date Modified:)
NTFS stores its time as the number of 100 nanosecond 'ticks' since 1601 (UTC time, btw) and Windows displays a time based on your timezone and DST.

FAT32 stores it's time as local time with 2 seconds accuracy (hence the results you are seeing) starting in 1980.
The local time is the current time "on the clock", so it is not aware of timezones or DST offset.

This usually gives no problems, unless DST changes or you move with computer+USB-disk to the other side of the world.

This issue will be solved when you use an NTFS formatted disk for your backups.

PS: Why FAT32 instead of exFAT? Do you run into compatibility issues?
(just curious..)

The files were all originally copied from the HDD to the thumbdrive, then synchronized via Directory Opus from that point forward. I have never been able to find anything that distinguishes the oddly behaving files from the rest.

Yes, File Explorer shows the same timestamps.

The best I can recall, I originally formatted the thumbdrives w/ FAT32 instead of exFAT due to a compatibility issue that is probably/hopefully now a moot point. But since none of the files involved are large enough to make a difference, I left well enough alone.

For completeness, I'll add that the issue has been the same with every thumbdrive I've ever had. The Internet has suggested several tricks, like removing the thumbdrive before the DST change, rebooting the computer after the DST change, then re-installing the thumbdrive, or any number of variations, w/o making a difference.