Oh, Crystal, you always give us so many options! Especially when it comes to formatting data types.
1. Right-click on any report object, select "Format Field".
If you're modifying a Number type, you'll see a "Number" tab. If you're modifying a Date type, you'll see a "Date / Time" tab. This is one of those instances when Crystal does a bit of "automagical" thinking for you. If you don't see the formatting options you expect, it's because the underlying data type isn't correct.
2. From the "Date / Time" tab, select your favorite Date Format. You'll see there are many options. I'm personally a big fan of XX/XX/XXXX, but must admit that XX/XX/XX also works well.
The biggest reason you'll probably want to go here is to select a formatting that omits the time precision portion of the date field. You'll probably need to re-size the field in question after the fact as well.
3. For those who are brave of heart, you may also click the "Customize" button. This gives you ultimate control over how a date is presented. Poke around a little; it's pretty interesting. You can use this, in some cases, to provide offbeat sorts and work in client-specific nomenclature.