Use postDate in section title format field
The entry will be passed to this template as a variable named object. When you want to reference its properties you have two options:


{postDate} (single braces)
{{object.postDate}} (regular Twig syntax)


The first one is just a shortcut for the second one. When Craft is getting ready to pass your Title Format template off to Twig, the first thing it will do is find any of those shortcut tags and swap ten with the full Twig syntax.

So in your case here's what you should do:

New Arrivals for {% if object.postDate %}{postDate|date('M j, Y')}{% else %}{{ now|date('M j, Y') }}{% endif %}