In which album are you viewing the photos? In "All Photos" the photos should be sorted by the capture time, but in Recents or Imports by the date the photo has been added.
To compare the dates of two photos, it does not suffice to to compare the date in the Info, look also at the timezone assigned to the photo. Photos is showing the timezone assigned to the photo only at the bottom of the "Image > Adjust Date and Time" panel.
When you import from different cameras at different times, Photos may set the timezones of the imported photos differently, depending on where you are, when you import the photos and whether the photos are having GPS assigned or not. (How Photos Handles Time Zones when Importing Photos in Photos 5 on Catalina - Apple Community)
- When you import photos with GPS tags, photos will use the timezone of the GPS location.
- If a photo has no GPS tags, Photos will use the timezone of the current system time zone of your Mac.
When Photos appear to be incorrectly sorted, I am changing the medium time format in the System Preferences, so Photos will show the time zone in the Info of a photo. How to display the Date and Time Zone in the Info in Photos in Catalina.
This way I can see directly, if tow photos have been assigned to the same time zone, or the time zone needs adjusting.
