Fix the month off by one error for #29

Change needs tested.

The range returned by getMonth() is 0-11, thus you need to add one 
for display purposes. Based on 
https://developer.mozilla.org/en-US/docs/JavaScript/Reference/Global_Objects/Date/getMonth
Merge pull request #57 from smsm1/patch-1

Fix the month off by one error for #29