In an effort to explain to six-year-old Clare how a time traveler's life works, Henry likens time to a tape recorder. First he describes normal life to Clare: "…you put in a tape and you play it from beginning to the end, right?… That's how life is" (1.3.96). Then he contrasts his life to that first version:
Now for me, it's different. Because I am a time traveler, I jump around a lot from one time to another. So it's like if you started the tape and played it for a while but then you said Oh I want to hear that song again, so you played that song and then you went back to where you left off but you wound the tape too far ahead so you rewound it again but you still got it too far ahead. You see? (1.3.99)
His analogy does a great job of showing how something as simple as playing a tape can quickly get out of hand if you lose your sense of beginning, middle, and end. Once you've lost touch with the when and where, it's very difficult to get back to solid ground again. Or perhaps, at some point, it no longer matters when and where you are in the tape – you just are.