I’m having difficulty understanding where the “message” comes from.

```
NSDate *now = [NSDate date];
NSLog(@"The new date is %@", now);
double seconds = [now timeIntervalSince1970];
NSLog(@"It has been %f seconds since the start of 1970.", seconds);
```

In the first part, if NSDate is the object and date is the message, then where was date defined/initialized?

In the second part, if timeIntervalSince1970 is the message, why can’t I use timeIntervalSince1980 as the message?

Any help would be appreciated, thanks.