Rolling 12 month total

[Nanaia]

How do you create a rolling 12 month total? I found a formula

=SUMIF(A$2:A2,”>=” & DATE(YEAR(A2),MONTH(A2)-11,DAY(A2)),B$2:B2)

but it sums 0.0000 (see screenshot) and I can't figure out what I did wrong.

 

[Fluff]

You have the wrong type of quotes, it should be

=SUMIF(A$2:A2,">=" & DATE(YEAR(A2),MONTH(A2)-11,DAY(A2)),B$2:B2)

 

[Nanaia]

Fantastic! Thank you. That's what I get for copying the silly thing and pasting it into my spreadsheet. It's the little things that count! Thank you again. I re-wrote the formula (using the correct quotation marks) and it works.

 

[Fluff]

You're welcome & thanks for the feedback.

 

[Nanaia]

I've discovered two things with this, on the 13th month this is not calculating correctly. It appears to only be going back 11 months. Shouldn't the total for D14 be 0.036?
I've also discovered the formatting for the month-year must be changed. I have to put the three letter designation of the month in column A and the four digit year in column B. How would I modify the formula to accommodate the change?

 

[Fluff]

For that formula to work col A needs to be actual dates not text & they all need to be the same day