Almost similar with https://gist.github.com/wilik16/ce6f3e96b90fd459da661c4e22be3c91, but this one is based on the photo's exif instead of the csv file from icloud. Unfortunately this script is still incomplete but almost complete.

icloud_photos_date_modifier_script.rb

# frozen_string_literal: true

require 'exif'
require 'time'

folders = Dir.foreach('.').select do |e|
  /^iCloud Photos/.match(e)
end

photos_paths = []
folders.each do |folder|
  photo_names = Dir.new("#{folder}/Photos").entries.reject do |e|
    /(^.*\.csv$)|(^\.)|(^\.\.)/.match(e)
  end
  unless photo_names.empty?
    photos_paths << "#{folder}/#{photo_names}"
  end
  
end
return

file_path = 'iCloud Photos Part 48 of 50/Photos/IMG_5768-1.JPG'
# file_path = 'Photos/IMG_97721.JPG'

data = Exif::Data.new(File.open(file_path))

puts data.date_time_original
puts data.date_time_digitized
puts data.offset_time
puts data.time_zone_offset

new_date = Time.strptime("#{data.date_time} #{data.offset_time}", '%Y:%m:%d %H:%M:%S %z')

puts new_date
puts File.mtime(file_path)