Consider the following output from exiftool running on debian stretch for an mp4 shot with a samsung android phone . In particular, note the filename indicates the clip was shot at 08:24 local time (the timezone -7 GMT, as indicated by the filesystem tag). However, while all the xmp and exif tags are in UTC they do not explicitly state that they are in UTC with the Z or "+00:00" convention. Is samsung violating the standard? Should those tags be in UTC by default, and, if they aren't, then attach a timezone +HH:MM ?
exiftool -a -G1 -s 20160509_082447.mp4 [/tt}
[ExifTool] ExifToolVersion : 10.15
[System] FileName : 20160509_082447.mp4
[System] FileModifyDate : 2016:05:09 08:24:56-07:00
[System] FileAccessDate : 2016:05:09 08:24:56-07:00
[System] FileInodeChangeDate : 2016:05:09 08:49:55-07:00
[File] FileTypeExtension : mp4
[File] MIMEType : video/mp4
[QuickTime] MajorBrand : MP4 v2 [ISO 14496-14]
[QuickTime] CreateDate : 2016:05:09 15:24:56
[QuickTime] ModifyDate : 2016:05:09 15:24:56
[Track1] TrackCreateDate : 2016:05:09 15:24:56
[Track1] TrackModifyDate : 2016:05:09 15:24:56
[Track1] MediaCreateDate : 2016:05:09 15:24:56
[Track1] MediaModifyDate : 2016:05:09 15:24:56
[Track2] TrackCreateDate : 2016:05:09 15:24:56
[Track2] TrackModifyDate : 2016:05:09 15:24:56
[Track2] MediaCreateDate : 2016:05:09 15:24:56
[Track2] MediaModifyDate : 2016:05:09 15:24:56
Does adding -api QuickTimeUTC fix the problem?
YES it does. The output becomes:
diff <(exiftool -a -s -G1 -time:all -api QuickTimeUTC 20160509_082447.mp4) <(exiftool -a -s -G1 -time:all 20160509_082447.mp4)
< [QuickTime] CreateDate : 2016:05:09 08:24:56-07:00
< [QuickTime] ModifyDate : 2016:05:09 08:24:56-07:00
< [Track1] TrackCreateDate : 2016:05:09 08:24:56-07:00
< [Track1] TrackModifyDate : 2016:05:09 08:24:56-07:00
< [Track1] MediaCreateDate : 2016:05:09 08:24:56-07:00
< [Track1] MediaModifyDate : 2016:05:09 08:24:56-07:00
< [Track2] TrackCreateDate : 2016:05:09 08:24:56-07:00
< [Track2] TrackModifyDate : 2016:05:09 08:24:56-07:00
< [Track2] MediaCreateDate : 2016:05:09 08:24:56-07:00
< [Track2] MediaModifyDate : 2016:05:09 08:24:56-07:00
---
> [QuickTime] CreateDate : 2016:05:09 15:24:56
> [QuickTime] ModifyDate : 2016:05:09 15:24:56
> [Track1] TrackCreateDate : 2016:05:09 15:24:56
> [Track1] TrackModifyDate : 2016:05:09 15:24:56
> [Track1] MediaCreateDate : 2016:05:09 15:24:56
> [Track1] MediaModifyDate : 2016:05:09 15:24:56
> [Track2] TrackCreateDate : 2016:05:09 15:24:56
> [Track2] TrackModifyDate : 2016:05:09 15:24:56
> [Track2] MediaCreateDate : 2016:05:09 15:24:56
> [Track2] MediaModifyDate : 2016:05:09 15:24:56
Thank you for responding to my question.
For further info, I think this is the thread (https://exiftool.org/forum/index.php?topic=3416.0) where this was first reported.
WOW. This is one complicated piece of software... to supposedly do something so simple! So many manufacturers and file formats doing things slightly differently each time... it's crazy. I'm so grateful that you've sorted through this crazy state of affairs.