Unfortunately, there's no way to view the calendar by month using Teams. Teams only supports displaying the calendar in day/week formats.
As a workaround, you need to view your calendar in outlook to see a month view of your calendar.
To get this feature more quickly, I have found feedback in Teams UserVoice, and you could vote for it. Many features of our current products are designed and upgraded based on customers’ feedback. With requirements like this increase, the problem may well be released in the future. Thanks for your understanding and support.
Feedback: https://feedbackportal.microsoft.com/feedback/idea/c150de6c-e46f-ec11-a81b-6045bd78dc6e
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