It’s possible to localize Company Calendar for Jira to any language assuming that the language is supported by your Server or Data Center Jira version.
1. Download the latest Server or Data Center version from Atlassian marketplace: https://marketplace.atlassian.com/apps/1217938/company-calendar-for-jira/version-history. You should download the file company-calendar-VERSION.jar.
2. Please open this file, using a zip archive program located on your computer.
3. Extract all the files into a new folder.
4. Go to the folder where you've extracted the files and open i18n folder.
5. Now, you need to create a file named according to the language you want to add. We suggest to copy English companycalendar.properties, put it into i18n folder and rename it to companycalendar_XX.properties where XX is a language code. Please check here https://en.wikipedia.org/wiki/List_of_ISO_639-1_codes for appropriate ISO 639-1 code.
6. Translate each property from the file, using a java properties editor. If you have Eclipse you can utilize Properties File Editor. Alternatively, you can use convenient tolls like https://java-properties-editor.com/ or https://github.com/jcbvm/i18n-editor. Please note that editing via standard text editor would not work as the property files need to be in ISO-8859-1 where all non-Latin characters are represented by \uXXXX where XXXX is a special code. You can use a standard editor. Only then, you will have to convert all the content using one of the online converters like: https://coderstoolbox.net/string/#!encoding=js&action=encode&charset=iso_8859_1 or https://itpro.cz/juniconv/
7. Some properties have {0}, {1}... text. These are the places where information from the application is injected. For example, for this property:
companycalendar.common.labels.sureDelete=Are you sure you want to delete the {0}?
{0} is replaced by the name of an entity being deleted. So, please be sure to position {X} accordingly.
8. Make sure that all properties are translated. As rule of a thumb, you can check that your resulting file has the same number of lines as companycalendar.properties file.
9. The property calendar.common.locale shall have a value according to the language code you require. Please refer to the fourth column, starting left, in the table to check the correct code. For instance, the code for Ukrainian language is "uk".
10. Go to the folder where you've extracted the initial jar file. Create a zip archive that contains all the folders and files from the current folder. Please make sure that the folders and files are in the root directory of the archive. Then, rename the archive to company-calendar-VERSION-XX.jar where XX is your language code. Please keep the created archive for your future references. Now, you can install the translated version via file upload. Please see: https://confluence.atlassian.com/upm/installing-add-ons-273875715.html
11. Please note that updating Company Calendar for Jira to a new version will require the file translation review and editing, based on the added text in the new version.