A large amount of my applications have the same Date Modified, Date Created and Date Added (eg App Store, Contacts, Dictionary, messages, photos, stocks, system settings etc)
The time stamp is for a time I know I wasn’t home. Is this just a software update I can’t find a record of?
What you describe is as expected. Some explanation:
The apps you mention (App Store, Contacts, Dictionary, messages, photos, stocks, system settings etc) are all included with macOS. For macOS 11, 12 and 13, macOS and its included apps are all part of the read-only signed system volume which holds all of the macOS (but not other apps, etc.) which you have installed.
The signed system volume is exactly the same on all Macs with the same version of macOS. Being exactly the same includes all file dates (creation, modified, added) being the same.
So it is to be expected that all these files will have dates that relate to when Apple created them. Nothing to do with when you did the installation or upgrade. "Date added" can be particularly concerning, but it is the date that Apple added it to the macOS which is identical on all Macs with that version of macOS.
You will have done the installation, upgrade or update some days or weeks later.
