See documentation here: https://docs.mendix.com/refguide7/parse-and-format-date-function-calls/
and here: https://docs.oracle.com/javase/7/docs/api/java/text/SimpleDateFormat.html
Use the current date time token to parse to month. So if you want the full name of a month as string use:
formatDateTime([%CurrentDateTime%] , ‘MMMM’)
Regards,
Ronald