Arnon,
I'm not really clear how you could have the wrong date in the EXIF, given that EXIF shouldn't be rewritten by anything short of deliberate (and probably unethical, to say the least) hacking of the original file's EXIF data. Now if your camera was set on the wrong date, I could see that, but the EXIF once set shouldn't change.
You said:
After I imported most of my items into new catalog and organized it
This implies that you were rebuilding a catalog already?
Anyway, there's no transparent way to force rebuilding of an entire iView catalog. The fastest way is to drag folders from catalog to catalog, rather than doing the reimport thing.
If your date fields that you have changed are an annotation field, rather than changing the actual EXIF data, then you can write that data to the files (thus making it permanent) by using the "Sync Annotations" command, under the Action menu, and using the "Export annotations to original file" option.