This would let users add the post to the categories without having to click on the post. Alternatively, instead of adding this feature to the page, it may be easier to add a link somewhere on the page to the search that would show the same results.

For example,

e621.net/post/popular_by_day?day=13&month=12&year=2017

could have a link somewhere on the page to

e621.net/post/index/1/date:2017-12-13%20order:score%20

The only issue with this is that the number of posts shown in the search is more than the 'popular' link. maybe this link could restrict that.