Adding cells based on the date

The best I can do is insert a formula in (say) col L to pick the months  =month(d2)

Copy all they way down the column

Then use conditional sum  formula    =sumif(L2:L1584,6,k2:k1584)

The 6 in the middle refers to the sixth month (June)

If you want a table for the months remember to use f4 to fix the ranges before you copy them