Print the Calendar of a Month

1. You have learned how to calculate the beginning day of a month, and how to print the calendar of January given the 1st day. Now combine these two skills to print the calendar of any given month.
2. This slightly differs from the task of printing the calendar of January, where January always has 31 days. You must determine how many days are there in a month, which you learned to handle with a switch statement in the homework of beginning day of a month.
3. Because the width of each month name may be different, if you want to center-justify the month name and your number, you can not always print 4 spaces in front of the month name, as you did for January.
4. For "May", you need 6 spaces. For "March", you need 5 spaces. So this depends on the width of the month name.
5. Therefore, you have to determine the month_width and year_width, and print (20-(month_width + 1 + year_width))/2 spaces in front of the month name.

2016 3
     March 2016
Su Mo Tu We Th Fr Sa
       1  2  3  4  5
 6  7  8  9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30 31