[digiKam-users] digiKam "date"s and times

[Gilles Caulier]

Hi,

Data and Time metadata handling is a complex problem as all metadata
container provide this kind of information.

Take a look in this C++ method which parse the date time stamp tags from
image metadata to populate the date i database :

https://cgit.kde.org/digikam.git/tree/core/libs/metadataengine/engine/metaengine_item.cpp#n536

As you can see, exif, or iptc, or Xmp are parsed. and if XMP side car is
present, it also parsed. And again this depend of the settings used from DK
metadata setup.

As ou can see this depend of plenty of cases, and it's a big puzzle.

The good news is : we have an advanced metadata configuration panel where
we can customize the source to handle metadata information. See Setup
DK/Metadata/Avanced view...

The bad news is : the date time information is not yet available in this
configuration panel.

We have a file in bugzilla about this topic :

https://bugs.kde.org/show_bug.cgi?id=382825

Best

Gilles Caulier

Le lun. 10 juin 2019 à 09:58, Jim Todt <jtodt at pacbell.net> a écrit :

> Hi.  digiKam newbie here.  Please bear with me as this may get a little
> long...
>
> I've started testing digiKam (6.1), looked at settings, looked at the
> website, docs, Nabble forum, & even tried reading some code.  But I
> haven't found the specifics I'm looking for... (Hopefully they're in a
> spec document or user document somewhere, and not just in the code...)
>
> digiKam makes reference to "date" often; and in one place in the docs it
> talks about "EXIF date" as being the 1st choice.  But even within EXIF
> there isn't just 1 "date"...  So what does "date" really mean?  digiKam
> seems to use "date" in at least 3 places:
>
> 1) Importing.  Which drives Properties & Metadata.  I seem to get these
> results:
>
> 1a) Properties->Photograph Properties->Created comes from
> EXIF-Spec:DateTime.  What ExifTool calls ModifyDate.  The last time the
> picture was modified (not created).
>
> 1b) Metadata->EXIF->Image Information->Date and Time also comes from
> EXIF-Spec:DateTime.
>
> 1c) Metadata->EXIF->Photograph Information->Date and Time (Digitized)
> comes from EXIF-Spec:DateTimeDigitized.  The time that the image was
> first digitized.
>
> 1d) Metadata->EXIF->Photograph Information->Date and Time (Original)
> comes from EXIF-Spec:DateTimeOriginal.  The "taken" time - when the
> camera shutter was actuated.
>
> 2) View menu sorting.  This seems to use the filesystem dates.
>
> 3) Left side Dates & Timeline.  These seem to use either the Created or
> the Date and Time above - in either case ultimately EXIF-Spec:DateTime.
>
> Hopefully someone(s) can help with these questions:
>
> a) Is the above correct as to what dates digiKam is using for what
> purposes?
>
> b) In a recent forum thread there was talk of a date needing to appear
> multiple times before it's used - is this correct?  If so, what is the
> reason for this rather than using each date per the spec?
>
> c) Why isn't the Original date used for sorting, selecting, etc.? As the
> "taken" date, this would seem to be the most appropriate choice rather
> than a date which can be changed later by other software...
>
> d) I think in the same forum thread there was talk of a coming ability
> for the user to specify what datetime fields should be selected in what
> order to be used for each purpose?  Is that correct?  If so, is there a
> timeframe for when this might be implemented?
>
> e) The latest EXIF spec includes Offset fields to (finally) include
> Timezone.  However, digiKam only lists 1 of the 3 EXIF Offset fields.
> Is this a work in progress?  Will digiKam include the other 2 (when?)
> and use these Offset fields to correctly sequence pictures from multiple
> Timezones?
>
> f) Is there a Best Practice for when & how to use UTC time in digiKam?
>
> g) Or is there some other Best Practice for how dates and times and the
> related fields should be handled in digiKam?
>
> Thanks for your help!
>
>
>
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