Old gas & how does a lawn mower generate spark & do timing?

Took apart the pull mechanism of my single-cylinder Craftsman push lawn mower today since it hasn't been used in a year and it wouldn't start in one pull and the recoil spring mechanism was not recoiling after the first pull (the cord just hung limp).

When I cleaned up the recoil mechanism & put it back together, I found some of last year's gasoline, and it worked just fine (so anyone who says you can't use old gas is gonna have to explain why it worked just fine for me today).

After two or three pulls with the choke locked open (otherwise it slides shut too quickly), the motor started and after about ten seconds on choke, I removed the clamp I put on the choke lever to keep it in place.

I cleaned out the air filter too and cleaned up old grass in the blade area (and a bunch of rope tangled around the driveshaft - I guess slowing down the blade is what makes the motor shut off since I defeated the shutoff mechanism due to it being a PITA as you always have to hold it on).

Anyway, my question is I started to wonder how the spark is generated, and I wondered how a simple (Craftsman) lawn mower advances its timing.