I utilized an off day from work the best way I knew how: hit the slopes
Arapahoe Basin has the longest ski season of any resort, typically opening around mid-October and closing as late as the fourth of July! For my 30th birthday, I did a half day at A-Basin and a half day at a water park (my birthday is June 10th). It was the most badass birthday ever, and only possible in the great state of Colorado.
I highly recommend skiing at A-Basin for the views alone. Skiing at the continental divide is an experience unto itself. Although the lifts are slower than other resorts in the area, the terrain is fun and varied.