My "Difficult" Daily Challenge today was to play a player-generated quiz within 20 minutes of it going online.

I don't think I've ever earned this one.

But on a whim, I went to the Buzz and saw a quiz that went online only a few minutes earlier.
I double checked the clock - the quiz went online at 6:55PM and it was 6:58PM or so FT time.

Took the quiz, got a 10/10, submitted around 7:04PM (that's NINE minutes since going online)

Yet - no credit.

update: perhaps the Buzz misleads and it didn't really indicate that the quiz went on line at the time stamp, just that it went online today?

Indeed that is the situation. A lot of times on the Buzz it'll indicate that a quiz went online today rather than when that message is generated. I have the same challenge today and have been clicking that screen every few minutes for hours but I somehow missed the 20 minute window for the three quizzes that got put online today. I don't like this challenge one bit. I traded it out two days ago so to spite me the system gave it to me again today.

Check on the homepage for when quizzes go online. Those times are accurate. You might have to change the homepage you use to get the one that lists new quizzes.