the sketch I'm working on might... I'm using processing to design a GUI for a laboratory... but then again, if it resets every 24 days I guess they'll turn the computer off on weekends so it's not a problem :)

If that's a concern, you can make your own millis() function not casting the long to an int:

1.   public long lmillis() {
2.     return System.currentTimeMillis() - millisOffset;
3.   }

That's just the PApplet's millis() without the casting and with tweaked return type. millisOffset is a long.

Ah, it is package protected. I overlooked that as most PApplet fields are public, in general...
Just declare:
long millisOffset = System.currentTimeMillis();
(or other name) as global variable, and you should get the same result.

Yup, now it's working :)