Calculate true/false and date

Hello,

I'm stuck at a DAX calculation. I need to calculate how many items are open in a column named "Closed". The open values have the status False. The value is linked to a field called "closuredate" and the date is set tot 31-12-9999. Example is below: 

How can i do this ? If i use the next dax i'll get the numbers in a table:

Openstaande meldingen = COUNTROWS(FILTER(Incident; Incident[closed] = FALSE()))

 

but when i use it in a visual and there is a date slicer it will return 0 because the closure date is 31-12-9999

 

 

Who can help me to solve this issue.