Add a 'Clear' option next to the two date lines in the challenges. This allows for quicker setup; 'Clear' is particularly useful when setting up an open challenge, reducing the process to just two clicks instead of changing six different drop-downs.

The attached picture also displays a 'set to today' option. Initially, I added this, thinking it could be convenient for a quick reset if you clear or change the dates. Maybe not necessary, but could consider including both for added flexibility?

*Also to be noted for clarification that my picture shows the date fields cleared but when you setup a challenge those a filled in with that days date.