The Daily Challenges are available during specific time periods:

• Morning Challenge: 12AM - 11:59AM
• Evening Challenge: 12PM - 11:59PM
  (The time of the Challenges corresponds to your local time zone)

Daily Challenge progress is saved to a monthly calendar that tracks completed Challenges and their accompanying Star rating. If you missed a previous Challenge or wish to try to increase a past Star Rating, you can do so by tapping on the specific date and paying the Coins to retry.

The Calendar resets each month and there is no way to go back and view or replay Daily Challenges from a previous months.