SUM, FILTER using a dynamic range to calculate Year to date (YTD) data

I'm struggling with a calculation to create a dynamic range to compare data from this year and the previous year for the same months. I believe I'm using the offset function wrong, but I cannot find a solution how to accomplish this. Maybe the offset function is a bad choice to calculate the YTD data.

The data is in columns, I know how many data is available in this year, so I need to calculate the total for the same period of the previous year. My guess was that this could be possible with OFFSET used as SUM(OFFSET(A1:A40;0;2), meaning that the calculation would be on the range A1:C40. To make things more complicated, the data must be filtered based on another column. I added the filter function for this.

Attached is a sample file with the formula's.

Can anyone point me in the right direction?

Art.

Cell C5 formula

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Cell C4 formula

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With 365, try:

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And:

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