I opened this GitHub issue for phpmyadmin. not sure if any of y'all know a path I can take.
https://github.com/phpmyadmin/phpmyadmin/issues/17604

tl;dr:
both phpmyadmin and myself use https://github.com/trentrichardson/jQuery-Timepicker-Addon
however, it is unmaintained and based off of jQuery and jQuery-UI
Unfortunately, I do not know of a replacement timepicker that supports milliseconds (or smaller potentially) and day of year. Any thoughts on what to do for this? I'm hesitant to make my own bc it seems a lot to remake from scratch but it is looking more and more that I may have to.