Geoff,
This pictures ingested by PM, modified/cropped by Lightroom, but nothing else done to it,i.e no caption.
$ exiftool -v /Users/kbaker/Downloads/DJI_0321.jpg
ExifToolVersion = 11.88
FileName = DJI_0321.jpg
Directory = /Users/kbaker/Downloads
FileSize = 3091896
FileModifyDate = 1591109466
FileAccessDate = 1591109470
FileInodeChangeDate = 1591109468
FilePermissions = 33206
FileType = JPEG
FileTypeExtension = JPG
MIMEType = image/jpeg
JPEG APP1 (17818 bytes):
ExifByteOrder = II
+ [IFD0 directory with 9 entries]
| 0) ImageDescription = default
| 1) Make = Hasselblad
| 2) Model = L1D-20c
| 3) XResolution = 240 (240/1)
| 4) YResolution = 240 (240/1)
| 5) ResolutionUnit = 2
| 6) Software = Adobe Photoshop Lightroom Classic 9.2.1 (Macintosh)
| 7) ModifyDate = 2020:06:02 08:35:44
|
ExifOffset (SubDirectory) -->
| + [ExifIFD directory with 31 entries]
| | 0) ExposureTime = 0.03333333333 (1/30)
| | 1) FNumber = 2.8 (28/10)
| | 2) ExposureProgram = 2
| | 3) ISO = 120
| | 4) ExifVersion = 0231
| | 5) DateTimeOriginal = 2020:06:02 03:44:51
| | 6) CreateDate = 1970:01:01 03:44:51
It is Lightroom that is making the EXIF CreateDate be 1970/01/01. I believe the reason this is caused is due to the original image on the card having embedded XMP with the following two key/value pairs:
xmp:ModifyDate="1970-01-01"
xmp:CreateDate="1970-01-01"
-Kirk