According to dev help it looks like you could... still use the TextEncrypted property and place a date in there. However, it is going to treat it as text, so you may lose out on functionality as a result.
If you want native support to encrypt a date property it looks like we do not have such a feature today. Just password, and TextEncrypted it looks like.
"Except as described here, Pega Platform treats the value of a TextEncrypted property similar to a Text property. Your application can place dates or numbers in the value, but validation does not occur."