Symptoms

Jira is displaying a mixture of different languages.

Cause

The known causes for this behaviour are:

1. Due to the way certain Java classes handle internationalization, some action words are dependent on the locale set by the JVM (which uses the system default locale). For example, if the default system locale is set to French but Jira's default language is set to English, some words will still appear in French.
2. One of the following Jira bugs:
   1. JRASERVER-28392 - The language translation got mixed up in the dashboard after choosing a default language other than the chosen one from initialization (fixed in Jira versions above 6.4)
   2. JRASERVER-46195 - mixed language in project administration
   3. JRASERVER-42361 - Inconsistent languages displayed in Activity Stream gadget

Resolution

Please follow the article Change Locale for Jira server and set the required language and country codes relevant for the Jira instance.