Hey @charlotteMARJ 

Welcome to the Klaviyo Community! Happy to help you with your product feed!

We use a “created_at” timestamp that is specific to Klaviyo. This means that when you first sync your catalog, every product in the catalog will have the same “created_at” value, so the newest products recommender will not be useful at first. Once you’ve added some new items to your catalog after the initial sync, you should start to see the expected behavior.

This also means that items will not be prioritized by the recommender just because they’ve been “updated” or have recently come back in stock. This recommender will only prioritize net new products added to your catalog.

Hope this helps!

Thanks Stephen 
very clear indeed 

I therefore chose the solution to set a “Newness” collection on my Shopify and to set the dynamic product feed only in this collection, to make sure the latest of my products are shown, no matter the synchronization 

Thanks again for clarifying 

Thanks for the explanation Stephen but that is not what we are experiencing. I am including a dynamic “Easter” collection in an email and, with the “Newest First” setting, products we uploaded to shopify 3 weeks ago are showing above products I added yesterday.
Where is your “Created_At” stamp taking its creation date from? Can I override it?