We're using Jira Cloud in German.

The field 'Start date' ist not translated to German (or any other language it seems). And it's also not possible to add a translation in the admin backend.

Key: 

Localization team update: i18n issue

JIRA Software creates several custom fields, and these fields are locked. Product should provide translation for these fields.
Since translation of custom fields does not harm these consistency, locked fields need to be translatable.

On Jira Software Cloud, when the user sets their language in account preferences, all system fields gets translated but Jira Software specific fields (Epic Name, Epic Link, Sprint, Start date...) remains in English. The field descriptions are partially translated for some of them (it still reads epic instead of “epica” in the middle of the sentence , for example), and not at all for others (start date).

Steps to reproduce:
1- Change account language and indexing language to a locale other than English
2- Create project
3- Go to Settings> Issues > Fields > Custom Fields
Here you can see that multiple fields are in English, and locked fields can't be manually translated by customer