Date format not showing correctly

Also, I setup a hint example one of the form field like (MM/DD/YYYY~MM/DD/YYYY). 

When someone leave the input section, it will out put (MM/DD/YYYY~MM/DD/YYYY).

How can I see just empty line for that?

Are you referring to this http://www.jotform.com/51276147758161 form? I see it is showing the correct format:

You can always change the format on the edit mode of your form by click on the date field, and change it with the Date Format button:

If you don't see any changes, try clearing your forms cache: http://www.jotform.com/help/229-How-to-Clear-your-Form-Cache

Let us know if you need more help, we will be glad to assist you.