It seems that 1.4 has a bug: the “time taken” is set to midnight in copies of the file that are exported. The Lightroom database and the original files maintain the correct time, but when you export a copy, the time is reset to midnight. It necessary to downgrade to an earlier version of Lightroom.
The Lightroom 1.4 update has been temporarily removed from the Adobe.com web site in order to allow time for additional investigation into several bugs that were discovered after the update was released. At this time, we recommend uninstalling Lightroom 1.4 and installing Lightroom 1.3.1.