Sum days/hours between multiple dates in excel with criteria

Hi there, my first post here and it's a bit of a complicated one! (at least for me). I've read everywhere and can't find an answer so any help would be really appreciated.

I'm trying to generate a report that shows the number of days any item is out of stock. The data I use is as shown in the attached.

As is, I use COUNTIF to count all the times any stock item is on zero, which is helpful, but it doesn't give me any indication of the amount of time it's been out of stock.

What I want the formula to do is instead of returning the number of times out of stock, it sums the length of time from 0 to >0 which could happen multiple times in the data.

Does anyone have any kind of starting point for me please?

Thanks in advance

Abe

Hello Abe1992 and Welcome to Excel Forum.
It may help if you upload a fictionalized .xlsx file similar to the one from which the screen shot is taken.
To upload a sample workbook click on the GO ADVANCED button below the Quick Reply window and then scroll down to Manage Attachments to open the upload window. Remember to include a few manually produced outcomes so that we will have a better idea of what you are looking for.
Let us know if you have any questions.

This proposal adds a helper column, which may be moved and/or hidden for aesthetic purposes, to Sheet2.
The helper column (G) is populated using: =IFERROR(IF(INDEX(C3:C$4108,MATCH(A2,A3:A$4108,0))=0,INT(B2)-INT(INDEX(B3:B$4108,MATCH(A2,A3:A$4108,0))),""),"")
The number of days out of stock is displayed in column F of Sheet1 using: =SUMIFS(Sheet2!G$2:G$4108,Sheet2!A$2:A$4108,B2)
Let us know if you have any questions.

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