Does my calendar have to be on a monthly view?

Your calendar is set by default to a monthly view. 

You can change the view to weekly or daily if you need to do so. 

Temporary change

Click the button to the right of the calendar (where it has the month and year) to week or day depending on your needs.

This will only change it for the current session of the calendar tab.

Permanent change 

To change it permanently, go to Settings > My Settings. In the upper right corner of My Settings, there is a Calendar tab. Go to the Calendar tab, select the view you need and click Save.