Update CreateDate (Video files more specifically mp4) with JSON information

[wywh]

To minimize confusion I'd suggest always using -api QuickTimeUTC when reading or writing movie dates (it has no effect in images and I use it if there are images mixed with movies). So check the dates with something like this:

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exiftool -a -G1 -s -fileOrder5 FileName -api QuickTimeUTC=1 -FileCreateDate -Time:All .
That way all times are forced to the computer's local time.

It has been a while since I uploaded movies to Google Photos but yes, there is one oddity:

-> Movies obey the Keys:CreationDate if it exists. .m4v and .mov display correct time combined with the timezone but in .mp4 the timezone must be subtracted from the time. I have wondered why .mp4 behaves differently but I just edit the time accordingly, if needed.

I have then had not much trouble chronologically mixing images and movies in Google Photos.

Google Photos reads the following related date and location tags. I prefer to use QuickTime:CreateDate and Keys:CreationDate for pre-1970 movies (dates before 1902 do not often work correctly in Google Photos). Corresponding UserData also work but macOS prefers Keys tags.

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[QuickTime]     CreateDate                      : 2001:01:01 12:00:00-05:00
[UserData]      DateTimeOriginal                : 2001:01:01 12:00:00-05:00
[Keys]          CreationDate                    : 2001:01:01 12:00:00-05:00
[UserData]      GPSCoordinates                  : 40.74842 -73.98561 443.2
[Keys]          GPSCoordinates                  : 40.74842 -73.98561 443.2
- Matti