Author Topic: Time Zone and Daylight Savings Time Struggles  (Read 298 times)

KingsCross

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Time Zone and Daylight Savings Time Struggles
« on: March 26, 2019, 11:34:39 AM »
I recently got back from a trip to Utah and Arizona and forgot to change the time zone settings on my Canon 5D Mark IV. Further complicating the situation is that my trip overlapped with the switch to daylight savings time. Besides dealing with the switch from MST to MDT, I then have to figure out how to deal with my photos shot in Arizona, which remains on MST.

I'm wondering if anyone has any suggestions for dealing with this.
Most of the examples seem to focus on shifting the -AllDates. But would you recommend changing the offset times, time zone, and daylight savings? Not totally sure how this impacts -AllDates. Or if changing the "Daylight Savings Tag" somehow messes with how some programs interpret the time zone offset.

Thanks for any insight you might have!

Code: [Select]
exiftool -a -G1 -time:all dir
[System]        File Modification Date/Time     : 2019:03:26 01:55:58-04:00
[System]        File Access Date/Time           : 2019:03:26 08:37:35-04:00
[System]        File Inode Change Date/Time     : 2019:03:26 01:55:58-04:00
[IFD0]          Modify Date                     : 2019:03:10 14:35:00
[ExifIFD]       Date/Time Original              : 2019:03:10 14:35:00
[ExifIFD]       Create Date                     : 2019:03:10 14:35:00
[ExifIFD]       Offset Time                     : -04:00
[ExifIFD]       Offset Time Original            : -04:00
[ExifIFD]       Offset Time Digitized           : -04:00
[Canon]         Time Zone                       : -04:00
[Canon]         Time Zone City                  : New York
[Canon]         Daylight Savings                : On
[ExifIFD]       Sub Sec Time                    : 00
[ExifIFD]       Sub Sec Time Original           : 00
[ExifIFD]       Sub Sec Time Digitized          : 00
[GPS]           GPS Time Stamp                  : 18:33:11.586
[GPS]           GPS Date Stamp                  : 2019:03:10
[Composite]     GPS Date/Time                   : 2019:03:10 18:33:11.586Z
[Composite]     Create Date                     : 2019:03:10 14:35:00.00-04:00
[Composite]     Date/Time Original              : 2019:03:10 14:35:00.00-04:00
[Composite]     Modify Date                     : 2019:03:10 14:35:00.00-04:00

Phil Harvey

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Re: Time Zone and Daylight Savings Time Struggles
« Reply #1 on: March 26, 2019, 11:47:48 AM »
Only Canon software has a chance of recognizing the Canon DaylightSavings tag, so you can probably ignore this one.

Setting the correct time zones is a good idea, but most software will ignore these.

By googling, it seems that most of Arizona observers MST all year, which is easy:

exiftool -alldates-=3 "-offsettime*=-07:00" DIR

but if you want to set some to MDT, then you would add something like this to the above command:

-if "$datetimeoriginal lt '2019:03:10 05:00:00'"

and run this second command to handle the pictures taken in MDT:

exiftool -alldates-=2 "-offsettime*=-06:00" -if "$datetimeoriginal ge '2019:03:10 05:00:00'" DIR

I hope this is what you wanted.  I'm assuming that your camera thought it was EST throughout your trip.

- Phil
...where DIR is the name of a directory/folder containing the images.  On Mac/Linux, use single quotes (') instead of double quotes (") around arguments containing a dollar sign ($).