This was at least partially fixed in LR 5.5, for images: Lightroom: Inconsistent dates for files missing date/time metadata. But I just tested importing a .avi into LR 5.7 / Windows 8.1, and the date under the thumbnail in the grid was the file system's last-modified time, while the Capture Date in the Metadata panel was set to the time of import.
I started a new topic in the official Adobe feedback forum: Lightroom: Still inconsistent capture date/time for videos. Please add your vote and opinion to that thread.
Whether it makes more sense to use date-modified or date-created (when date-taken is missing) depends on you, and file-type:
Date-created is more appropriate for DNGs and JPGs etc., since date-modified changes every time you save xmp or preview, if you do.
Date-modified is more appropriated for proprietary raws, *IFF* you're not modifying them externally..
Dunno 'bout videos..
If I were you, I'd bite the bullet, and round up all photos without date-taken metadata, and assign one (using Lightroom, or exiftool, or a script/plugin which harnesses exiftool..), even if estimated. - problem solved for you, by you, right now, and forever..
PS - If you want to flag all photos whose date is estimated, don't let me stop you - e.g. keyword, user-comment, label, etc..
You're right, photos seem to work okay in the newest version at least. I'm still trying to test and get my head around the inconsistencies in video import dates.
I do need to work out how to mass update the "date taken" in photo EXIFs though without touching photos that already have that field. Putting every photo I have into one folder, and sorting by date taken in Explorer to weed out the ones that lack it, and then doing date modified > date taken with EXIFtool is about all I can think of. Kind of messy.
You can use John Ellis' AnyFilter plugin to find all photos whose capture date is missing.
Or if you prefer, (my) SQLiteroom (free) will create a collection of photos missing capture date each time you start up.
I use exiftool to modify the Creation and Modification time of the files. After that I use LR "Ajust time" feature to set the time of the movies in LR to the file creation time (last point). This works fine for me.
For MOV (Quicktime):
exiftool "-FileModifyDate<TrackCreateDate" "-FileCreateDate<TrackCreateDate"
exiftool "-FileModifyDate<DateTimeOriginal" "-FileCreateDate<DateTimeOriginal" *.avi
Depnding on your camera (and container format mov, avi) you may also ajust the time zone, e.g.
exiftool -FileModifyDate+=1 -FileCreateDate+=1 -if "$CameraModelName =~ /EOS 600D/i" *.mov
Which time in the container (MOV, AVI) you use as source, depends on your workflow. I edit my mov files before import. Therfore "CreateDate" is the time when I edited the file. Quicktime and (some) avi file contain a time when the containing stream was created. I use this vaule as source.
exiftool <filename> gives you detailed information about all available times.
Thanks for the detailed info. Exiftool seems like a very powerful tool. I wish videos had a proper date taken like photos though... but having said that, I noticed Exiftool actually does list a date taken for AVCHD videos from my A6000. I'm just not sure if any program will use that info (Photo Mechanic does not, for one).
I wish videos had a proper date taken like photos though...
Modern video formats do have well-defined metadata formats -- LR just doesn't implement them. See Comparison of container formats - Wikipedia, the free encyclopedia.