A few minutes ago, the birth date did not show up when editing profile. Now it does again, but now the site claims valid dates have invalid months ("Please enter a valid month.").
Update (from my comment below):
After testing a hunch I had, I can confirm that it seems to only affect me with my current date settings under "Localization" (https://www.geni.com/account_settings/localization).
I have "YYYY MM DD" set as the "Input Date Format". The other two options work without any problem, so something is broken with the "YYYY MM DD".