I checked other questions here about this, but either the date/time numeric formatting has changed since the answers were given, or something else is wrong because the numbers they're using are 17 digits, and the ones I see in the bookmarks.html file are all 10 digits. e.g.:
<DT><A HREF="https://www.amazon.com/gp/aw/contact-us/ref=hp_gt_comp_cu#csp" ADD_DATE="1672512521"
Does anyone know if there's a Google Sheets formula I can use to convert these 10-digit dates in the exported bookmarks.html file to something like yy-mm-dd hh:mm:ss format?
You can use the EPOCHTODATE
function.
=EPOCHTODATE(1672512521)