IF statement for DATEDIFF to handle an error

Anonymous the SWITCH statement is internally converted into nested IFs but its much easier to write and read :smileyhappy:

DaysToClose = 
SWITCH (
    TRUE (),
    'Opportunities'[ClosedDate] < 'Opportunities'[CreatedDate], -1 * DATEDIFF ( 'Opportunities'[ClosedDate], 'Opportunities'[CreatedDate], DAY ),
    'Opportunities'[ClosedDate] > 'Opportunities'[CreatedDate], DATEDIFF ( 'Opportunities'[CreatedDate], 'Opportunities'[ClosedDate], DAY ),
    0
)

This should do it!

EDIT: I guess I didn't see this in your original post => When this error occurs DaysToClose =0

If by this you mean when the error occurs value should be zero you can modify the above column like this...

DaysToClose 2 = 
SWITCH (
    TRUE (),
    ISBLANK('Opportunites'[CreatedDate]), 0,
    'Opportunites'[ClosedDate] > 'Opportunites'[CreatedDate], DATEDIFF ( 'Opportunites'[CreatedDate], 'Opportunites'[ClosedDate], DAY ),
    0
)

The first formula will give you the differnce between Created and Closed:

+ difference if Created is before Closed and

- difference if Closed is before Created

plus you'll get blanks if either date is blank

The second formula will give you ONLY the + difference if Created is before Closed all else will get 0.