Craig Toomy: Oh I'm real scared now.
Nick Hopewell: Do you ever watch Mr. Spock on Star Trek?
Craig Toomy: What the hell are you talking about?
Nick Hopewell: Because if you don't shut your cakehole, you bloody idiot, I'll be happy to demonstrate his Vulcan sleeper-hold for you.
Answer: Think of time as a gear with only one tooth, and think of them as a gear with only one notch. In the past, the one tooth has forever passed their notch and they'll never be carried along in the flow of time again. In the future, the tooth comes along, snags their notch, and they're back in the flow of time.
Phixius ★