Illustrative example. The dates and amounts below are provided for practice.
A reversed input can produce an error that looks like a missing result. Suppose the intended interval is May 10 through August 20, 2024, but the two dates are entered in the opposite fields.
Confirm the problem
Set Relationship Start Date to August 20 and Calculate Until Date to May 10. Calculate. The form reports that the end date must be on or after the start date.
Do not expect a negative “days together” total. This tool describes a span beginning at the relationship start, so the reversed interval is rejected.
Repair with the original information
After checking the dates, enter May 10 as start and August 20 as end. Calculate again. The result is 102 elapsed days and inclusive Day 103.
This distinction matters when copying the result. The error is about chronology, while the one-day difference between the two valid outputs is about whether the first date counts.
If August 20 actually is the relationship start and May 10 is a prior memory, keep them as two separate events. Swapping fields only makes sense when the values were transcribed into the wrong places.