Out of curiosity, a brief analysis has concluded that there is a 'regular' combination of different days. It seems, at a glance, that 2 x 5 is the most numerous, three second, and three last). There is a very useful website that gives about the next 50 yrs of calendars!
To use it in point of fact, 2018 holds the highest combination of most that I have seen thus far.
Where the 824 yr. thing comes in I do not know, so can only email the person who emailed me about it in the first place this am.!