http://www.geocaching.com/geocache/GC3DPF6_the-100-100-star-challenge
"For this challenge you will need to accumulate 100 Difficulty Stars and 100 Terrain Stars in a single day. At a minimum this could be completed with 20 caches all being 5/5 caches or at most with 100 caches all being 1/1. You may complete it with whatever combination you wish but all the caches must have been found in a single day."