You can change the date format in extra fields in DJ-Classifieds.

Let’s add the custom field with date

For sake of this tutorial I’ll create the “Availability” custom field that will be used for showing the availability for the apartments.
Open DJ-Classifieds in back-end and click “Add field” and set:

1. Label name
2. Tooltip description if you want to use one
3. Type (I chose “Date” but you could also use “Date from-to” if it better fits your purpose)
4. Date format in PHP format (if nothing entered it’ll use the default Y-m-d format) - in this tutorial I’ve used the date format: F j, Y, g:i a

NOTE: You can set more settings than I did. Learn more about adding custom fields - https://dj-extensions.com/faq/dj-classifieds-faq/how-to-add-new-extra-field-in-dj-classifieds
Click Save.
Once saved you can assign the extra field to chosen category

Now the field was added to “Apartments” category.

Once adding the advert from front-end to this category, the date field will be displayed and user will be able to select the date from regular calendar with icon (1):

then select the date from the calendar (2) and the date will be displayed in the field (3).