WORKAROUND SOLUTION TO APPLE IMOVIE DATE/TIME SHOWING WRONG INFO
I ran into this as well, but here are the workarounds I've found so I can at least use the time/date stamp text feature to display the correct time.
How to add a time and date text overlay to your video
1 - Drag clip into your project
2 - Cick the "T" button to add a text title.
3 - Drag the Text Title called "Date/Time" to the clip that you want to burn a timestamp to.
4 - Preview the clip and write down the time and date iMovie is adding to the video if the info is wrong.
Steps to get Apple iMovie to burn in the CORRECT time and date:
5 - Select the video clip in your project that you added the date/time filter title to and choose, show in event browser (this is a Control+click or right mouse click option).
6 - Under iMovie's File menu choose "Adjust clip date and time..." Please note that you are adjusting the metadata in the original movie inorder to fool iMovie. If this clip is also used outside of iMovie you may want to do this on a copy of the movie.
7 - Enter in the offset from the time displayed to the time and date desired. In most cases you can simply click the hours backward to get to the correct time zone offset.
8 - Scrub the video clip with the Date and Time Text filter and verify that it now shows the desired time.
If you are needing to put in a timestamp with seconds you will probably need to use another video editing tool to burn your timecode in. Apple Motion and Adobe After Effects gives users the ultimate control in adding this meta data along with font choices, colors, etc, but it is probably overkill for most users!
References:
http://commons.trincoll.edu/sta/2012/07/06/adding-a-timestamp-to-your-imovie-fil e/