All files out of sync by 12 hours, meaning that FFS thinks that every single file needs updating

[e1ijah]

My FreeFileSync seems to have a time detection error. It is detecting that every single file on my backup drive has a file timestamp 12 hours earlier than is actually the case. So after doing a Comparison, FFS is saying that *every* single file on my backup drive needs to be updated. This would take hours to do.

The time detection error on every file is offbase by exactly 12 hours, which can't be a coincidence and must be clearly an error in FFS. For example, a file on my computer that is timestamped "Date: 19/10/08 19:26:14" is timestamped "Date 19/10/08 07:26:14" on my backup drive.
This all starting happening after I updated my OS --- which involved completely deleting all files from my computer and then copying all my files back from a backup drive after the new install. THe backup drive from which I copied all my files back onto my computer is the only backup drive that is unaffected (because of course the timestamps match). But all my other backup drives are affected by this 12 hour problem, which effectively renders FFS very difficult to use, since every Comparison shows that every single file need to be updated.

I have tried using the option whereby FFS compares files on the basis of File Size rather than File Time and Size, but this is not ideal and would create other problems (it would possibly lead to file loss further down the line in the future, since two files can be the same size even after the original is updated).

Any advice to fix this would be appreciated.

[Zenju]

Sounds like: https://freefilesync.org/manual.php?topic=daylight-saving-time

[e1ijah]

At first, I thought so too. But there's nowhere on earth that has a 12 hour daylight saving shift.
I could indeed set FFS to ignore a 12 hour daylight saving shift. But that would mean that FFS would not be updating new files unless 12 hours have passed. There would be a 12 hour window all the time in which I could lose my files. In other words, I could work on a file on my computer all day long --- and still lose that file even after running FFS if the computer crashes within 12 hours of my working on it, since FFS would have ignored the new file as not having been updated.
I can live with a 1 hour shift, but not the above scenario of a 12 hour error.

[Zenju]

I could indeed set FFS to ignore a 12 hour daylight saving shift. But that would mean that FFS would not be updating new files unless 12 hours have passed. There would be a 12 hour window all the time in which I could lose my files.

That's not how it works. See the note on the linked page.

Anyway, the real solution is for you to find out what was causing the 12 hour shift (hint: it was not FFS).

[TAC109]

Check your OS time zone. Also check your clock is correct (a.m vs p.m.).

[e1ijah]

Ok thanks. My computer seems to be on the correct time settings and correct time zone, i.e. it says that the time is 14:30 when it is indeed 2.30 pm in my timezone. However my new OS seems to only allow 24 hour time formats, perhaps that is the cause of the problem. (But if that's the cause of the problem, surely FFS should be able to accommodate operating systems that do this, i.e. that don't require am versus pm?)

I've set the daylight saving shift to 12 hours. But I've discovered that there are quite a few of my files that are off by 13 hours -- presumably these are files that were created during the six months of daylight savings in any particular year. But it might be more manageable now, given that there are fewer of these 13 hour files --- the amount of time that FFS says it requires to update all these files is down to 45 minutes rather than 2 days.

[e1ijah]

Also: Suppose I permanently set FFS to a 12 hour shift from now on. Would this mean that I'm screwed again when daylight savings rolls around in my time zone? Because I would then have one set of files that are 12 hours off, plus another set of files that are 1 hour off due to daylight savings. If I understand it correctly, FFS would only ignore files with an exact 12 hour shift, if that is what I have set it to. But what happens then with the new set of files that are 1 hour off?

[TAC109]

You can supply a comma-separated list of displacements to be used in the 'ignore time-shift' field (see the example below the field in the link above).

[e1ijah]

Ok thanks very much for the help, I think that has worked. I've set the daylight savings time shift to 1, 12, 13.
Still not sure what caused the 12 and 13 hour shift in the first place.

[TAC109]

Some operating systems store file times as local time, and others store file times as GMT and apply the region time displacement when showing. As you have changed OS types it may be that they recognise file times differently.

[e1ijah]

ah ok, much appreciated.

[therube]

I updated my OS

What OS is that? (And maybe even locale, for that matter.)

my backup drive

And what drive?