Calculate Days between two dates - only for the current month

Hi DennisJung,

Based on my test, you should be able to follow steps below to get the expected result in your scenario.

1. Add a YearMonth column in your Date table if you don't have it yet.

YearMonth = YEAR('Date'[Date])*100+MONTH('Date'[Date])

2. Use the formula below to create a new measure.

Measure = 
VAR firstDayOfMonth =
    MIN ( 'Date'[Date] )
VAR lastDayOfMonth =
    MAX ( 'Date'[Date] )
RETURN
    SUMX (
        Table1,
        VAR s =
            MAX ( Table1[Start], firstDayOfMonth )
        VAR e =
            MIN ( Table1[End], lastDayOfMonth )
        RETURN
            IF ( s < e, DATEDIFF ( s-1, e, DAY ) )
    )

3. Show Name column as Rows, YearMonth column as Columns, and the measure as Values on the Matrix visual.

Here is the sample pbix file for your reference. :smileyhappy:

Regards