Why View Parser Filter not working on Loop Substitutions ?

Your missing the quotes on the date.

Code:

{blog_entries}
        <div>{post|date('d-m-Y')}</div>
{/blog_entries}

Try that if it doe's not work then something else is wrong, hard to tell without see more of the code.

I am just starting to try CI4 and I ran into the same problem. And - no, the problem is not with the quotes, the same filter works fine without quotes if out of the loop. And the loop works fine if the date filter is not applied on the date.