Counting dates and blank cells

Hello,

I want to have the number of the open inquiries for a specific month, some of them have been closed and there's a closing date and some of them are still open and the date cell is empty.
For instance, for January I have 15 open inquiries, I use count if to count the inquiries open in and before January and closed after January. I can easily find the inquiries closed but I cannot figure out how to add the open ones too (blank cells). I have tried many formulas for blank cells counting but couldn’t find a working solution or maybe I should change formula...?


A B C
Inquiry Open Closed
Inquiry 1 08/10/2015 12/05/2017
Inquiry 2 04/02/2016 09/05/2017
Inquiry 3 18/05/2016 27/03/2017
Inquiry 4 06/01/2017 21/03/2017
Inquiry 5 24/01/2017
Inquiry 6 19/01/2017 03/02/2017
Inquiry 7 20/01/2017
Inquiry 8 29/12/2016
Inquiry 9 23/12/2016
Inquiry 10 22/12/2016
Inquiry 11 28/11/2016
Inquiry 12 10/11/2015
Inquiry 13 21/06/2016
Inquiry 14 17/03/2016
Inquiry 15 10/09/2015

I use COUNTIFS (B:B;"<=31/01/2017";C:C;">=01/02/2017") but I cannot find the 3 criteria, to count the blanks too. C2:C16;"" for instance is not working.

I hope you can help, thanks!

Try this ...

=SUM(COUNTIFS (B:B;"<=31/01/2017";C:C;{">=01/02/2017";""}))

See this ...

All good. I forgot I was in other language and had to change the formula titles...