What exactly is your use case?
Generally you can use [%BeginOfCurrentMonth%] and [%EndOfCurrentMonth%] to see if a date is in this current month.
e.g. if you want to retrieve all objects with a date of this current month saved, you could use a retrieve action and this XPath → (date > [%BeginOfCurrentMonth%] and date < [%EndOfCurrentMonth%]). This returns the objects whose dates are after begin of current month and before end of current month.
Or maybe you want a text to be visible once today is only 5 days away from the end of the month (e.g. when you want to remind the user that they need to do something before the end of the month).
Then you could use this XPath for text visibility on a page → (daysBetween([%CurrentDateTime%], [%EndOfCurrentMonth%]) <= 5). The text will appear only if there are less than or exactly 5 days between the end of the month and it could maybe say: “Submit your work before the end of the month”.
I hope this was helpful
where $yourentity/yourDateattribute >= ‘ %BeginOfCurrentMonth%]’ and $yourentity/yourDateattribute <= ‘[%EndOfCurrentMonth%] ‘