Month pages can be used to mark an event, such as introduction of a character. It is not limited to just that however.
If you are going to edit these pages, please respect the layout and notice that dates fall in ascending order that means January 1st will be above January 2nd and so on. The years are different, they are in descending order so 2011 will be above 2010 and so on.
You can link these pages from your page or anywhere else simply by using the brackets [[January]]. Please, do not remove information without stating your reasons.