Six, according the USA Today. Actually, that’s only in season enders. She also saved the world in midseason, in episodes “Innocence”, “The Zeppo” and “Doomed”. And technically last season, it wasn’t Buffy that saved the world, but Xander, and Giles. So she’s saved in eight times, so far. I’m guessing number 9 is coming in the next couple of weeks.