On This Day Query Explained

{
 ; Set Title
 :title "⌛ On this day..."
 ; Get all blocks
    :query [:find (pull ?b [*])
       ; We want to filter on Today, so we get that variable as input (See input)
       :in $ ?today
       :where
       ; Now to filter, first, we only want journal pages
       [?b :block/page ?p]
       [?p :page/journal? true]
       ; Then we fetch the Day of the Journal page, store it in ?jd
       [?p :page/journal-day ?jd]
       ; Tricky part, but what happens it turns date into string
       ; Not sure, but I assume unix timeformat so YYYYMMDD
       ; Then use subs to cutoff the YYYY
       [(str ?jd) ?jds]
       [(subs ?jds 4 8) ?md1]
       ; Then we do the same trick for today
       [(str ?today) ?td]
       [(subs ?td 4 8) ?md2]
       ; What we are left with is a compare of Today without year, matches pages
       ; without year
       [(= ?md1 ?md2)]
       ; Finally filter out today, as that's not history....yet
       [(< ?jd ?today)]
    ]
    ; Make Logseq provide todays date
    :inputs [:today]
    ; Why yes we want to see the year
    :breadcrumb-show? true
    ; And show me everything unfolded
    :collapsed? False
}