I catalog images by the date each was taken.
I do too. It really sucks when the camera has the wrong date time stamp. In that case, it the EXIF data you need to modify - see (Solved) Change "Date Picture Taken" with Image::ExifTool.
I would recommend checking the return of utime since it may fail. I also agree with the other comment that perhaps you want to warn and not die. You might also want to consider not updating the time stamp unless it is different.
I am kind of interested in what tool you use to organize your pictures that depends on the timestamp of the file and not the internal Exif data. I personally have written my own tools but I completely ignore the file time stamp and don't run into the problem you are having.
Cheers - L~R
In reply to Re: Change Image File Timestamp to Match EXIF Data