Blank date field updating as 12/31/1969 instead of NULL

I have date fields in my sql tables that can be blank and is set to have a default value of null. When I update the table with the date fields left blank, the value 12/31/1969 (or 1969-12-31 in sql table) is saved in the database. I’m not doing any date formatting on my input fields and the dynamic data, if present, is not formatted as well. How can I keep those fields blank if nothing is entered? Below are snap shots of my sql table and form. I have the same issue whether I run a multi-update or a single-record update.