you state that you need to use a database function, which is untrue, and you seem to be answering part of the answers supplied.
Try my solution, it should fix it immediately.
As for using a database side solution, consider that NOT posting your database type NOR the version of Crystal requires guesswork by others.
If you want to use a SQL Expression, then use whatever the syntax is for your database to convert it to a date first, simple stuff really.
Whatever the database is, DON'T use a to_char (I assume that you're using oracle), convert the char based date field to a date and just use crystal to format it. if you return a date as a text element, you will lose lookup, grouping and sortation capabilities on that field.
If you insist on doing so, then post in your database type forum here for the syntax for returning what you need as this is a database function question, not Crystal.
-k