Add up total amount of occurrences of zero per month

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Hi,

I've asked a couple of question recently and this forum has been so helpful, thanks so much.

I'm having another problem, I've got a table of data, in the first column I have the dates 1st January 2015 all the way up to 31st August 2016 and on the top row I have the USER ID numbers of some customers and in the table each cell represents the power usage of each customers on that day. I've added a final column on the right which works out the average data usage of the users that day excluding users that didn't use any power

My first problem is that I want to create a function that can work out the total amount of zeros that appear in each month (January 2015 being different to January 2016) so in this example for April 2015 the result would be 2.

My second problem is that if possible I would like the function to ignore days that contain zeros for all users (in the average column they have the value #DIV/0!). So for January 2015 I'd get the result 2 as well. If somebody could help me with this it would be fantastic.

Thanks in advance