I came home from my first cross-country Amtrak experience with a whole bushel-basket full of pictures. Much to my consternation, I discovered that the camera’s date and time settings were almost 5 days behind. After much investigation, I decided that jhead was the best way to fix the problem. So, here is the jhead command I used:
jhead -da2012:11:09/13:52:04-2012:11:04/19:59:04 *.jpg
This translates to: “jhead -da(correct date/correct time)-(wrong date/wrong time) fix anything with a .jpg filename in the current folder” (I probably could have just used * without the .jpg, because in most of my picture folders, only the jpegs have metadata.)
I determined the correct time from a photo that included my Tom-Tom GPS, which was stuck on the train window. I brought it for the entertainment value of knowing how fast we were moving, and where we were. By the way, from Florida to Washington, D.C., the max speed was usually right around 80 mph. From D.C. to Philly, on improved tracks and with electric engine, the max speed was more like 110 mph.
Jhead calculates the difference between the two date/time entries, and adjusts every date/time entry in the exif metadata by the calculated difference!
Then, because I rename my pictures by the exif date/time, I used the following jhead command to fix the filenames:
jhead -nf%Y-%02m-%02d_%02H-%02M-%02S *
Next time I have a metadata issue with jpegs, I’ll look carefully at jhead’s documentation page FIRST!
Lin-u-Type 