All month names are translated according to the instructions. You did not understand the question.
Please do the following:
1. Go to http://obninsk2.ru/hotel
2. Look at the reservation block with the date selection.
3. You see the English name of the month (Feb), despite the fact that all abbreviations and month names are already translated through Poedit.
4. Click on any date in the calendar.
5. You see how the name of the month began to be displayed in Russian (because it is translated into Russian through Poedit).
You have a bug, the month is initially displayed in English, the language changes only after selecting a date.
Please give me your website url and admin credentials and ftp information.
Let me check it.
Best Regards,