Apologies if this was already found out or known, but i found the popular by day page, it was a bit hidden in all the pages: https://e621.net/explore/posts/popular
Topic: Found the "Popular By Day" page.
Posted under Site Bug Reports & Feature Requests
Oh, i thought it was just changed to the 'Hot' page
It's still on the sitemap. I think it was a small oversight that led to why the option isn't on the hotbar now.
Oh good, I like the popular page. I hope it stays