What wrong with 31st May?
When loading some GPX files recently I could not get the time stamp to appear when using " Feature Information / Vertex list and on saving all the time stamps were lost. After some investigation I think that the date 31st May is the problem. I have attached 3 short files. Test file-01 loads and works Ok, file-02 which has 31st May in one record will not display the time stamp and when saved ( file-03 ) all time stamp information is missing.