I'm afraid there is no such example. This is more of a business requirement question rather than a grid feature.
javascript Date object can help you to get dates in a given month and year.
e.g., (new Date( 2013, 2, 0)).getDate() returns number of days in Feb 2013 which you can use to fill colModel.
and (new Date( 2013, 2, date)).getDay() returns weekday which you can use to create nested colModel of a parent date column.