Just a small thing, but minutes and seconds in the inspector panel always mirror each other, and when you try to change one, the other will change as well. It effectively means you cannot have accurate seconds, unless for some strange reason you wish to prefer accuracy of seconds over minutes. 
I’m not seeing that. Which date are you editing? Could you give a specific example of what you did and what you saw?
All three (Created/Added/Modified) exhibit the same behaviour. I’ll dig a bit deeper and see if I can find out what condition is causing it. It might be a system date format thing. I’m not using anything really bizarre, just YYYY-MM-DD HH:MM (24h).
How can Added exhibit the behavior when the Date Added isn’t editable?
While you cannot modify Added, it still exhibits the behaviour in the numbers that it produces. Minutes and seconds always mirror each other, no matter when you import or create the file. An example set of Date Added timestamps from my library:
- 2008-12-16 13:56:56
- 2008-12-11 19:16:16
- 2008-11-09 18:33:33
It looks to me like the time format in your International preferences pane is incorrect. Perhaps it’s configured to use <Minute>:<Minute> or <Second>:<Second> instead of <Minute>:<Second>.
Interesting, good catch. I did have a double-entry in one of the format options. The rest were fine, which is seemingly why this behaviour wasn’t showing up in other applications; or rather it would have if they had selected the display option you were using. Otherwise, I probably would have solved this a lot earlier.