I hadn't noticed this incongruity, thanks for letting me know. I checked the web and unfortunately there are conflicting data. ll 1987 is associated both on 23/24 October and 19 December. I assume it's not an easy and accurate calculation, each country then has its own specific debt with the planet. For example, this year Italy's overshoot was on May 8, 2018, anticipating the global one. However I believe that despite this incongruity, the problem of consuming in advance the resources available on our planet must be contained and somehow solved. Thanks a lot for reading my post.