A Date Based Challenge cache is a type of Challenge Cache.
Date based challenges follow a theme of finding caches based on some date. Variations that exist include:
There is a variation that exists where you have to find 100 geocache's in the series by 2013. As of 2012 you are not able to create this type of date based challenges due to changes in the Challenge Cache guidelines. Groundspeak felt that challenge caches must be reasonably obtainable by anyone who wants to pursue them. If such a challenge existed for 2011, anyone who joined after the start of 2012 would never be able to complete the challenge, making it unobtainable to a growing population of geocachers.