Which self am I?

I have lots of questions about the world every day.

• Where did I put my keys?
• Is my phone battery dead?
• Is there enough food in the fridge that I don’t need to go grocery shopping yet? (Maybe you can tell what kind of life I lead right now.)

But one of the most common questions I ask is also—I’d say—the most profound:

• What time is it?

Those other questions are all about some feature of the universe: if I could unroll a big 4-dimensional map of how everything is, was, and will be, I could give an answer. But asking “What time is it?” is not asking something about that map, it is asking where I am on it. It is asking: Among all my past and future selves, or at least, those selves in an interval consistent with the information I have,

• Which self am I?