Script to adjust the EXIF date of an image file by a given offset in days.

adjust_exif_date.rb

#!/usr/bin/env ruby

require 'open3'
require 'time'

EXIF_DATE_FORMAT='%Y:%m:%d %H:%M:%S'

offset = ARGV[0].to_i
file_name = ARGV[1]

raise "Can't find file #{file_name}" unless File.exist?(file_name)

file_date, status = Open3.capture2('exiftool', '-p', '$DateTimeOriginal', file_name)
raise "Failed to read date" unless status.success?
file_date.strip!

date = DateTime.strptime(file_date, EXIF_DATE_FORMAT)
new_date = (date + offset).strftime(EXIF_DATE_FORMAT)

puts "#{file_name}: #{file_date} => #{new_date}"

output, status = Open3.capture2e('exiftool', "-DateTimeOriginal=#{new_date}", "-CreateDate=#{new_date}", "-ModifyDate=#{new_date}", file_name)
raise "Failed to set dates: #{output}" unless status.success?