Re-processes all photos when DST changes

[rprieto]

I have a collection of 4000 photos which exiftool-json-db keeps updating with no issues.
However the day after daylight savings ended (from GMT+11 to +10), it wanted to re-process all 4000 photos.

One example in the existing metadata.json was

"SourceFile": "2014 April/2014-04-02 10.00.23.jpg",
"File": {
  "FileModifyDate": "2014:04:02 09:00:22+11:00",
}

which seems wrong given the filename (Dropbox) should be accurate. Comparing FileModifyDate above and the actual file mtime, they are indeed off by an hour, which explains why exiftool-json-db wanted to re-process it.

Once it had re-processed all files and saved the database, the entry then said

"FileModifyDate": "2014:04:02 10:00:22+11:00"

So why was 2014:04:02 09:00:22+11:00 OK during daylight savings (even though it seems wrong)? Why is it all of a sudden off by an hour after DST? These timestamps should be DST-agnostic given they have a timezone offset in them.

This sounds like the same old issue as thumbsup/thumbsup#16

[rprieto]

Update: this could be unrelated to exiftool-json-db. When doing an AWS sync to S3, it also picks up all these files to be 1h off, and wants to reupload them:

• the file is already on S3, last uploaded on 2015-10-16 00:40:13+11:00
• because it was synced with s3cmd, it also has the original mtime as metadata: 1444914356000 which is Fri Oct 16 2015 00:05:56 GMT+1100 (AEDT) (so, modified about 45min before it was uploaded)
• when running aws cli sync in 2017, the day after daylight savings, it read the mtime on disk as being 2015-10-16 01:05:56+100:00, which is 1h later than the original mtime stored on S3
• because mtime is now later than the "last uploaded date", S3 re-uploads the file

This might point to an issue with macOS, or with the disk driver, as it's happening outside of exiftool-json-db.