Trending on custom entity data

Hello, 

I want to create trending reports from custom entity's data. We have some import automation that updates the data (keeping record Id as it is) daily and the need is to create Historical trending for this data set. Since we have a daily update on the same data set, definitely copying all data day-by-day wouldn't be a good option. 

Can anybody suggest me on how to achieve this? 

Thanks, 

Sandip