Code Kata: A simple text-based calendar

In this Kata we want to properly display a simple calendar view of a given month. Let's start with an example. A proper output of our program for the input data of "December, 2013" would be:

Mo Tu We Th Fr Sa Su
                   1
 9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31

Points to consider:

• how many times we need to make a call to time-date functions?
• try to minimize the number of these calls
• try to separate program logic from presentation as much as you can