How to use the blog post published date in a search web part

I have a page with a search web part that shows the latest blog posts. The problem is that it shows blog posts with publish date in the future. I just want to show posts where publish date is less than, or equal to, the current date. I tried with PublishedDateOWSDATE<= {Today} but this is not working. I found that PublishedDateOWSDATE has format text, so that won't work.
Is there another date (with date format) I can use, or can I convert PublishedDateOWSDATE to date format?

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Ona Nyhus