Ok let's start this over from ground-zero (so to speak of course).

I haven't used datedif in so long, I had to do a full read on it, and found using the md syntax, all it is doing is subtracting the days and pays no mind to the months. So in example 1 of 02 Jan to 16 Mar, it would show 14, but that is absolutely wrong to real time. It just does 16 minus 02. Terrible formula!! That's why I stopped using it. Being you have physical dates in both cells, do a simple Sum(end date - start date) to get the true value of 73 days, which translates per the 30 day scale as 2 months and 13 days.

The same stands true for the second date set of 02 Apr and 19 Jun. If you use datedif md, you get 17 smashes keyboard but simple end-start returns 78 and converted to 2 months 18 days.

Total combined time is 4 months 31 days (independently totaled) which converts to 5 months 1 day. And if you add the 73 days and 78 days, it returns 151 days which also converts to 5 months 1 day.

What I need is a better understanding of where you came up with 5M 4D in total. There is a 3 day discrepancy which is completely throwing me off.