Counting rows/incidences between date columns

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How it works  ...

Create relationships

Create dax measure ...

ValidCount = 
VAR mindate = MIN('Calendar'[Date])
VAR maxdate = MAX('Calendar'[Date])
VAR mysubset = FILTER(Facts,Facts[Start_Date] <= maxdate && Facts[End_Date] <= mindate)
RETURN
CALCULATE(
DISTINCTCOUNT(Facts[ID]),
mysubset
)

Create report ...

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