My phone is providing incorrect information about the date time of the image. If I change the date and time in the Geotagging tab, it is reverting to the original incorrect data, and I am unable to enter any data in the other fields. How do I change it in Darktable. The manual does not help much. Thanks to anyone who can guide me on this
You need to use something like exiv2 or exiftool of you want to permenantly alter the metadata.
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Not only that, there are at least three different date tags in the exif, so it would be best to know which one is used for “the date time of the image”.
Can’t help personally - I don’t use darktable.
To my knowledge (date / time when image was taken)
[EXIF] 0x9003 Date/Time Original : 2022:08:24 19:49:14
For correcting this date/time with exiftool read : ExifTool by Phil Harvey section Date/Time Shift Feature
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You might also check first what the difference is.
It is possible that it’s just a difference of interpretation: one using local time, the other UTC (the expected difference in such a case would be a fixed number of whole hours, if you have something like 17 minutes, there’s another reason times are off).
If you indeed need to correct dates and/or times, why not correct all in a file by the same amount? At least the different time stamps stay consistent…
For some hardcoded image data I use the hex editor. But that’s an overkill if you are not sure what you are doing. It works 100% of time though.
You might try the image_time script:
when enabled it adds the utility module that allows you to adjust or set time non-destructively within darktable
@martin.scharnke this lua script would be really useful when scanning photographs as long as you can remember the year the original was taken. It also looks promising for when we travel and forget to set the camera to local time.
Which was exactly my omission for my recent flying (both short and literally by air!) visit to New Zealand
I sail to New Zealand on the 28th of January for about a two week cruise. Hopefully some wineries will cross my path during shore excursions.
Raise a glass 
or 
for me! Also note that February 6 is a public holiday in NZ (Waitangi Day), and not without some controversy.
I am in Auckland for that day. I guess we have the controversy of Australia Day and they have Waitangi Day.
All my cameras are UTC everywhere. Here are the reasons:
- You can’t forget to set the timezone
- EXIF has no concept of timezones, it just has “a time”
- Even if some manufacturer has a tag, that is not compatible with anything
- During travel you can cross multiple timezones, change would have to be immediate
- It gets worse with the international date line
- Timezones suck
Sure, matching up images with others is extra work but that can be automated. Also it only concerns output so it is repeatable as often as required. Editing RAW files themselves is something I avoid at all cost.
I was lucky to talk to a journalist in the early days of digital cameras and he was totally furious after doing a story where he crossed a border with a timezone switch MULTIPLE TIMES A DAY. He changed his cameras to UTC during that gig. I did the same and had one less place to worry about timezones ever since. 
This sounds a great suggestion as I have reached an age where I am travelling a lot. Thanks for the suggestion.
Great script … this allows me to put more meaningful dates on my scanned material.
This sounds a great suggestion as I have reached an age where I am travelling a lot. Thanks for the suggestion.
I’ve been doing that too.
Reason being that stupid Digital Photograph Review adds “GMT” aka UTC to the end of their EXIF date string.
Can lead to comments that my Central Time USA daylight shot date is wrong.
The main problem is that the designers of EXIF forgot to add any kind of timezone/timeshift into the format. So only your camera knows about the zone you set it too, the file contains “time”.
Probably the same folks that designed how Windows treats the hardware clock of a computer.
It get’s even more confusing if you try to understand what happens when you try to set the camera time with gphoto2 unless the camera is set to UTC. Fun times! 
from the Exiftool docs :
0x882a TimeZoneOffset int16s[n] ExifIFD (1 or 2 values: 1. The time zone offset of DateTimeOriginal from GMT in hours, 2. If present, the time zone offset of ModifyDate)
Of course, that doesn’t mean all camera makers use that tag…
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Thanks for the hint … I just dug through the EXIF standard docs and it seems the following tags were introduced in v2.31 of the standard in 2016 [1]:
OffsetTime
OffsetTimeOriginal
OffsetTimeDigitized
These were not in the previous standard from 2012.
Given that a new camera takes around 2 to 4 years to make from first sketch to announcement I would expect the earliest cameras with such a feature to be from 2019. If you have a very adventurous manufacturer.
Not going to hold my breath on this one.
[1] https://cipa.jp/std/documents/download_e.html?DC-008-Translation-2016-E pg.49
That TimeZoneOffset tag comes from a TIFF specification from 2000, where it is marked as an optional tag. The same document defines the (mandatory) DateTime tag. And a lot of the EXIF tags seem to originate in TIFF.
So that particular tag exists since 2000, but seems not to be used by manufacturers (