How many hours have I spent in Skyrim?

Since all copies of Skyrim uses steamworks, Steam will keep track of how many hours you've spent in the game, assuming you have been online while playing.

If you go to your profile, you'll see your playing time to the right of your profile.

If you have been offline most of the time, then there is another way to very roughly estimate your playing time:

When you are loading your character, there is a series of numbers beneath the name that looks like this:

031.57.15

The first 3 digits represents the number of hours, the middle 2 the minutes, and last 2 the seconds. That is how 'old' your character is. This doesn't keep track of reloads, however.

If you add all these values up across all your characters, you can estimate your playing time.

For console gamers, the amount of hours played shows up under the information about your save file on the load/save files screens.