Oven/pizza update

Thanks to the suggestions on trying an oven thermometer. I bought a cheap one and found out my oven is hotter than it's supposed to be, for some reason. At 425 degrees it was about 445. At the 350 range it was close to 10 degrees off. I made my yummy pizza Friday night and set the oven at 405 degrees and the pizza came out perfect.  I hope this doesn't mean my oven is going whacky - it's not that old, maybe 5-6 years old.