Help with Calculating Monthly Average in a New Column

[Viz_kid]

Hello, 
I am trying to get the monthly average in a new column for each month, as shown in the image. Can someone tell me how can I achieve this, any help is appreciated. 

Regards,

I want to recreate the right most column

[ChiragGarg2512]

@Viz_kid , is the average required side by side to every date or the requirement is only getting the average.

[Viz_kid]

I want to show it side by side with every date. So January's monthly average next to all the dates in January, and February monthly average is next to all the dates in February and so on.