Use a date time item if entering a date using a calendar popup is useful.
If the date field is read only, typically a text box item with an appropriate 'Read Only Filter' setting is a better choice.
If another type of item should be used instead of the initial item created (text box should really be text area for example) simply change the item type at the top of the property window.
Options
Item type drop down list (top of property page): Allows changing this item to a different item type.
Format String: Determines the format of the date presented to the user. Click on the 'Format Help' button for help entering the desired format string.
Format Help: Provides help to build the desired 'Format String' value.