How to change date format for SIT from FND_DATE4_REQUIRED to FND_STANDARD_DATE without affecting old

Hi,

I setup self-service to allow users to update their SIT. However, I encountered an error about the date format FND_DATE4_REQUIRED. Because of this, I updated the segment's value set to FND_STANDARD_DATE. This worked for self-service, however, this affected the old date entries of the SIT. I also get an error when I try to revert to FND_DATE4_REQUIRED about the format being obsolete.

My questions now are:
1. Is there a way to help me revert the format to FND_DATE4_REQUIRED?
2. Is there a way for me to use FND_STANDARD_DATE and fix the changes made on the old SIT entries?