The regular Daily Challenges have undergone a bit of a rework. These improvements all apply to the Elite Dailies as well, so everything should be nice and consistent.
You'll only get one chance to set your leaderboard score now; you can try again as much as you like, but the repeat attempts will only be practice scores for your benefit only.
The reset time for the Daily Challenge is now at Midnight UTC every day, instead of midnight in your local time. So everyone will switch to the new daily at the same time.
Challenges can now also choose randomly between the Survival and Countdown modes, and we've improved the loadout selection so that you'll get a much better spread of random equipment when trying out every daily. Remember to check which mode the challenge is running for the day in the menu while checking what your loadout will be!