This is an idea for a possible improvement to the 'Needed Found Dates' page of the site.
I only have one date on which I haven't found a cache, that being the 29th February because there hasn't been a 29th February since I started caching and I have to wait until 2016 for the next one. I do, however, have approximately 60 days where I have only found one cache. I was wondering whether it would be possible to have a grid similar to the one displayed on the 'Map DT Matrix' which shows not only the days where you haven't yet found a cache, but also the days missing in the next 'loop'. For example, days with no caches could be coloured red, days with the next lowest count (in my case 1 cache) could be coloured yellow and all other days could be coloured green.
This would give cachers the challenge of finding caches on certain dates to complete their next calendar loop and lead to another statistic of the cacher with the highest number of caches on 366 days of the year.