Change your display language to something different from English (i.e. Hungarian).
Go to Control Panel -> Calendar
Create a new event check the start date's month. In Hungarian it is "január".
Move your mouse over the month combo box. It changes to "January".
It is a general prblem with date's month combo box. You can find it other places, for example: Control Panel -> Recent Contents -> Add -> Sales Presentation
It is not possible test on trunk, because the trunk version has a language changing error.