DC stands for "Day Change" as most of you know. These challenges are also referred to as "Semi-Live challenges" because they require minimal effort every X amount of hours. Similar to Castings where you have to play 1 challenge every 12 hours, DC challenges will be no different.
The main thing you need to know about DC challenges, is when the DC actually is. Look in the week's itinerary for the "DC Time." This will tell you how long you have to complete each action. DC Challenges are mostly to break down "Weekly Challenges" into little portions so no one is overwhelmed by what they see. A little effort here and there meets Live and Weekly challenges halfway.