In the SalesLogix web client if you want to add a column that is a DateTime column to a lookup control's lookup dialog you need to define it in a specific way in order to have the lookup make sense for end users.
If you define the lookup column as a PropertyType of System.DateTime, when a user attempts to search, the system will not interpret the user input correctly unless it is entered exactly as YYYYMMDD. If you format it as something like MM/DD/YYYY, the system will convert that to a different value during the search.
The way you want to define things are:
- PropertyType= System.String