Calculate different values based on today's date (last 30 days sales, last 60 days sales, lifetime sales...etc)

Calculate different values based on today's date (last 30 days sales, last 60 days sales, lifetime sales...etc)

Hi everyone, 

I'm looking to obtain something simple like "last 30 days sales", "last  60 days sales" as a value to use it on my pivot table.
I'm trying to get the following aggregate values : 
- Last 30 days sales
- Last 60 days sales
- Last 90 days sales
- Last 180 days sales
- Last 365 days sales
- Lifetime sales

This all based on the current date in order to have the most accurate information being updated regularily. I need to take in account of the increase or decrease in sales of a certain item. 

This will help me calculate the following values : 
- Sales velocity/day (= "last 365 days sales" / 365)
- Sales velocity/month (= "last 365 days sales" / 12)
- Stock cover in days (="actual stock" / "sales velocity/day")
- Stock cover in months (="actual stock" / "sales velocity/month")

And ultimately being able to forecast the needed stock to never be out of stock again. 

Hope someone can help me.
Regards, 
Marc