When you print invoice, all numbers and dates are formatted using default settings of your operating system (decimal and group separators, date structure). But sometimes it is needed to use language culture of your target customer from a different country. To achieve this, do the following:
1. Open Reference data > Customers, and open necessary customer.
2. Go to the Main customer settings tab and find Default formatting language field.
3. Select desired culture and save settings:
4. Try to print any document (for example, invoice), for that customer (screenshot is made on the system with default Russian locale):