Hello Klaus,
here’s how the events work:
UFO Week: Usually takes place once a month, around the last week of the month. During this week, at least one UFO = unfinished object should be completed; then you receive the title UFO King / UFO Queen.
Best of Leftovers: If you want this title, you need to use up as much leftover yarn as possible during the relevant period.
Yarn Diet / Yarn Emperor/Empress: This is about reducing your yarn stash (including whole skeins) that you have at home. Wonderful projects come from this, and you can buy new yarn. Normally the event only runs for four weeks.
Some of our users / designers have been consistently reducing their yarn stash for months, and of course that deserves extra applause.
Where do you still need more info?
There’s also more info here:
Final sprint and awards ceremony for March projects / Best of Leftovers / UFO Week
March Projects: All Easter and spring designs UFO Week March 21–28 Yarn Diet:
Final Round for World Domination Tunisian Crochet Continues
Best of Leftovers