This graph shows the global average score of each characteristic per day. There are 5 different characteristics all mapped unto a scale of -1 to 1. This value represents the average value of that day, regardless of which year it was. Therefore, this graph can show us the difference in people's personality throughout the year. The graph seems quite stable, except for a few peaks. For example, the most fluctuating time is during Christmas. Furthermore, there is a peak on conscientiousness and emotional stability around May 24th, but this date does have any significant meaning that could explain these peaks.
Using the range slider, you can have a closer look at any desired range. By hovering your mouse over the graph, you can see the exact date your mouse is pointing at and how many samples there are on that specific day.