Timeshift with Winter- / Summertime

[abgestumpft]

Hi,

I have imported some Fotos today/yesterday (Wintertime UTC +01:00 on PC) from several days ago (Camera Settings on Summertime UTC +02:00).

Now it seems that {File.MD.Exif::Main\36880\OffsetTime\0} is set by iMatch to current PC Setting UTC +01:00.
Therefore also the time taken is shifted by one hour:


The fotos taken after daylight saving changes (camera UTC+01:00) then the correct time is shown.

When I change setting Metadata2->XMP Import->Apply time-zone = NO (was set to "yes" before) and do a Reload Metadata / Force rescan, the date/time shown is correct afterwards.
But OffsetTime is still on: +01:00
Changing offset time in iMatch does not work: I see in ouput panel that exiftool applies "-EXIF:OffsetTime=+02:00", but afterwards it's right back to +01:00 in iMatch.
Also when I change the OffsetTime=+02:00 manually with exiftool and do a reload Metadata in iMatch afterwards,  Offset Time is updated to +02:00. But then the meta-data writeback-pencil pops up. As soon as I do a writeback of metadata, the Offset Time changes back to +01:00 (I don't see any OffsetTime parameters in exiftool output panel)

My questions would be:
1. Is it recommended to have Apply time-zone setting to NO ?
2. How is this OffSet Time calculated in iMatch? What I don't understand is that it's currently always being overwritten to +01:00 (PC TimeZone), also when I manually changed it to +02:00 with exiftool before.

[Mario]

Now it seems that {File.MD.Exif::Main\36880\OffsetTime\0} is set by iMatch to current PC Setting UTC +01:00.

IMatch does not modify EXIF tags directly.
It only updates XMP date and time tags. The mapping from XMP to EXIF is done by ExifTool during write-back.

Please read How IMatch uses Date and Time Information, especially the section about time-zones, time-zone offsets in files, File.DateTime being in local time always etc.

Also when I change the OffsetTime=+02:00 manually with exiftool and do a reload Metadat

Don't.
When you set datetime created, create time in the MD panel, the time-zone offset will be stored in XMP and mapped to EXIF and eventually existing time-zone offsets in EXIF. This is usually automatic.
When this fails for some of your files, the files probably have some metadata mess that needs fixing first. Use the Metadata Analyst to check and when you know what the problem is you will know what to fix.

[abgestumpft]

ok thanks, I will dig into this.

What wonders me at the moment is that OffsetTime was changed from +02:00 to +01:00 (either by iMatch or Exiftool). I guess that happened while iMatch applied the Timezone of my PC (which is different from the Foto timezone)

The file on SDCard (not changed) has Offset: +02:00

Code Select Expand

"D:\Dokumente\Downloads\Programme\ExifTool\exiftool-12.33\exiftool.exe" -G1:3:7 -S F:\DCIM\107OLYMP\PA300445.ORF | findstr -i time
[ExifIFD:Main:ID-33434] ExposureTime: 1/200
[ExifIFD:Main:ID-36867] DateTimeOriginal: 2021:10:30 09:14:11
[ExifIFD:Main:ID-36880] OffsetTime: +02:00
[ExifIFD:Main:ID-36881] OffsetTimeOriginal: +02:00
[ExifIFD:Main:ID-36882] OffsetTimeDigitized: +02:00
[Olympus:Main:ID-2312] DateTimeUTC: 2021:10:30 07:14:11
[Composite:Main:ID-Exif-SubSecDateTimeOriginal] SubSecDateTimeOriginal: 2021:10:30 09:14:11+02:00

The file that was loaded into iMatch has OffSetTime: +01:00

Code Select Expand

"D:\Dokumente\Downloads\Programme\ExifTool\exiftool-12.33\exiftool.exe" -G1:3:7 -S Y:\Fotos\PA300445.ORF | findstr -i time
[ExifIFD:Main:ID-33434] ExposureTime: 1/200
[ExifIFD:Main:ID-36867] DateTimeOriginal: 2021:10:30 09:14:11
[ExifIFD:Main:ID-36880] OffsetTime: +01:00
[ExifIFD:Main:ID-36881] OffsetTimeOriginal: +02:00
[ExifIFD:Main:ID-36882] OffsetTimeDigitized: +02:00
[Olympus:Main:ID-2312] DateTimeUTC: 2021:10:30 07:14:11
[GPS:Main:ID-7] GPSTimeStamp: 20:14:03
[Composite:Main:ID-Exif-SubSecDateTimeOriginal] SubSecDateTimeOriginal: 2021:10:30 09:14:11+02:00
[Composite:Main:ID-GPS-GPSDateTime] GPSDateTime: 2021:11:06 20:14:03Z


When I read the iMatch Docu about TimeZone: https://www.photools.com/help/imatch/#tech_exifdate.htm

File.DateTime has no time-zone.
By default, IMatch applies the local time-zone when producing File.DateTime from metadata

If I understand it correctly, I can prevent iMatch from applying the local timezone of my PC to the {File.DateTime} parameter by setting: Metadata2->XMP Import->"Apply time-zone" = No. Seems like it will use some other value then (Date Subject Created incl. its timezone if I understand the docu correctly)

Isn't it better to have set"Apply time-zone" = No?
Otherwise the Date/Time shown depends on the PC settings (and not the one from the camera). So it makes a difference ({File.DateTime} shifted by 1h) whether I import the photos in summer or winter time.

[Mario]

IMatch applies the local time-zone (or not, depending on your settings) when it imports date and time and sets the global File.DateTime.
It does not change the EXIF time-zone offsets or the time-zone offsets which are used in XMP.
During write-back, it writes the created/date subject created timestamps 'as-is' (as you see them in the Metadata Panel). XMP uses integral timestamps, for EXIF ExifTool splits the XMP timestamps into the separate date and time and time-zone offset tags.

If you modify the two XMP timestamps in the MD panel and write back, the ExifTool output panel shows what IMatch is sending to ExifTool.

[abgestumpft]

I will leave  Metadata2->XMP Import->"Apply time-zone" = "No" for now. Not sure if there is a catch, but to me it's much more logical to not use the local system timezone here.

For Offset Time ({File.MD.Exif::Main\36880\OffsetTime\0}) -> this one is always set to PC Timezone during metadata writeback (also when no time parameters are changed at all) I just did a metadata writeback (only RegionInfo and InstanceID) of a file that had Offset Time=+02:00. -> after Metadata Writeback the Offset Time was changed to=+01:00

[Mario]

Does the XMP timestamp you write contain a time-zone? Check in the Metadata Panel (click on it).

[abgestumpft]

Yes, the timestamps have timezone included:


I also found some older fotos without timezone in XMP Metadata. But also here the OffSet Time is set to +01:00 now when I save some metadata here (could be any metadata, must not be related to date/time):

[abgestumpft]

AHHHH 

This is correct:
Offset Time = {File.MD.Exif::Main\36880\OffsetTime\0}
36880 = 0x9010

From Exiftool Docu: https://exiftool.org/TagNames/EXIF.html
0x9010   OffsetTime   string   ExifIFD   (time zone for ModifyDate)

So timezones work correct: "Offset Time Original" is for Date/time taken, and "Offset Time" is for Modify Date/time!

Regarding the time shifted in iMatch when PC Timezone<>Camera Timezone, for me the solution should be to go with Metadata2->XMP Import->"Apply time-zone" = "No" to have correct time displayed in iMatch ({File.DateTime})