if you are in a Linux terminal and you want to quickly view a calendar you can use the simple cal command. Cal is part of the util-linux package.
If no arguments are specified cal will display the current month.
To display the calendar for a specific month of a year type:
cal month year
To display the calendar for a whole year type:
To display the calendar for the previous, current and next month type:
Here is the output for all the above comands.
If you want to read the manual page of cal type: