Date picker in Release dialog on new Releases page shows "undefined" when language is set to German, French, or Japanese

Steps to reproduce

1. Make sure the new project-centric sidebar is on
2. Set your profile language to German, French, or Japanese (Spanish and English seem to be unaffected)
3. Go to a specific version in a project (/projects/ONE/versions/<id>)
4. Click the Release button
5. Click the Date Picker icon to choose a release date

Expected result

The date picker shows properly and allows you to select a date

Actual result

The date picker looks like this:

Workaround

Manually type the date in, rather than using the date picker.