Returns a number from 1 (January) to 12 (December) representing the month.
A date in datetime format.
An integer number indicating the number of the month.
If the argument is a string, it is translated into a datetime value using the same rules applied by the DATEVALUE function.
Learn more about MONTH in the following articles:
Correct calculate of age in DAX from birthday
By answering to a student question I realized we often used a wrong calculation of customers age in DAX, and the simple solution is to borrow the same technique used in Excel, using INT and YEARFRAC rather than DATEDIFF or other divisions by 365 or 365.25. » Read more
Other related functions are:
Contributors: Alberto Ferrari, Marco Russo
MSDN documentation: https://msdn.microsoft.com/en-us/query-bi/dax/month-function-dax