Hi, had the same problem earlier this week, and changing the Spreadsheet Settings outlined here solved the issue for me. https://docs.glideapps.com/all/reference/components/pickers/date-time#date-formats-and-locales
For some reason, both my Locale and Time Zone were both set to London, even though I live in the U.S. So, I changed them both to U.S. (where I live) and problem was solved.
Here’s another place in the documentation that talks about this: https://docs.glideapps.com/all/reference/using-sheets/sheets-faq#im-having-problems-with-date-and-time-formatting
Let me know if this works…