Formula to add sums of cells based on date.

Hello everyone, I'm kind of new to Excel, and I have a kind of complicated task I wanted to complete. I'm not really sure if it's reasonably possible to do. But if you have an answer I would greatly appreciate it!

I have attached my excel file with my question for you. Basically, I want to add up the sum of the cells from column B in column C, based on which month column A is.
So each time there is a new day, next to that day in column C I want to add up the total sum of the value of the cells in column B for that same day.

It sounds confusing but hopefully the attachment will make it seem less confusing.excel example.xlsx


Thanks!

EDIT: I actually found a solution to the problem I was working on. I still don't know the answer to the question above, but I kind of worked around it. If you still want to answer my question, I would still be curious to know what the answer is, thanks.