Here are a few thoughts.
In iMovie 08 you can click VIEW/PLAYHEAD INFO. Now, as you skim with your cursor over a film clip, you can see the metadata (date and time)
My AVCHD camera does not know what time zone it is in. I set the date and time. When I go to a different timezone, the camera does not know unless you manually reset the time. I just checked some clips I shot in Turkey. They are mid-afternoon, but my camera thinks it is early morning.
Your AVCHD files are basically computer files, meaning they will have a creation date and a modified date. This is not the same as the date the clips were shot. This is the date they were first added to the computer.
So how do you know when the footage was actually shot? This is done by the way the camera names the clips. Your clips will have a name like clip-2008-01-01 13;05;30.mov. This means that the clip's first frame was shot on January 1st 2008 at 1:05 PM (and 30 seconds). This time comes from the camera date and time setting.
If all you have are the .mts files, you will not have this information at all. The .mts file contains the video clip. There is a different file within the file structure of your camera that contains the date and time. This information is used during import.
In Final Cut Pro X, you have a little more visibility of the metadata, and you can add your own metadata. But even in FCPX, all that gets imported are the Date, Time, Duration, Audio Sample Rate, Codec, and Camera Name.
