While there is no Clock app on a Mac yet, you can use the Calendar to set an alarm for any time on any day. By adding an Automator script, you can have that alarm play a sound at full volume or speak some text.
When you export photos from the Photos app the date of the file doesn't match the date the photo was taken. This is correct as the file is new and the photo in it does retain the metadata with the original date. But if you want to force the file date to match the photo date, you can do it in the Terminal or with an Automator app.