If you happen to be lucky enough to ski so many days that they are hard to keep track of, try this trick to get a good count of each one.
1. Head over to www.ifttt.com and create an account. If this then that lets you build 'recipes' based on actions that happen in the web or cloud.
2. Install the IFTTT app on your iPhone and set it up for location tracking.
3. Create a recipe that fires each time you and your phone enter into a geo radius based around your local ski hill.
4. Once you have the rule set to fire when you get to the ski hill, just decide how you want to record the data. In my case i just update my google cal to show a ski day
That is all there is to it. QED. The hard part is finding a lifestyle that lets you get too many ski days to count...