On This Day page dates are broken

My On This Day page is a little broken. Turns out that when I made the change to ISO dates, I broke the dates on this page. I implemented this page about a year and a half ago. It uses an external JS code, over at https://github.com/cleverdevil/micromemories, and my guess is that the American date format is built into the code, and there’s some sort of conflict between the way my dates are displayed now and how this code sees dates. I have an idea of how to fix this (there’s a Hugo code that should work in the help forum) but I’m not sure how to implement it (I’m guessing some sort of partial HTML file) and more importantly, where. If I try to place the code directly in the page, it shows as plain text. For now I’m leaving the old code up, as the page itself is still functional, and the dates of the posts on it are obvious enough (it’s called “on this day” after all), it’s just the year that is unknown - until you click on the post and it opens in its own page.