I was particulary impressed with the level of checking done in the exiftool command line program.
An old, scanned photo broke my not very good checking today with " : : : : " as a datetime original
I have
if ($dto =~ m/(....):(..):(..) (..):(..):(..)/ ) {
so I need to beef that up.
But exiftool picked it up
exiftool -Datetimeoriginal-='0:0:0 1:30:0' b00017test.jpg
Warning: Invalid time string ( : : : : ) when shifting DateTimeOriginal - b00017test.jpg
Alan