frequencies for a year prior for data with dates and frequencies

#1
I have a data set with two columns; These are the date and the frequency of surgeries on that date. Dates are only listed if the frequency of surgeries on that date was above 0.

I'd like to create a third column that gives the total number of surgeries performed within a year prior to the date.

Does anyone know how to implement this in SAS? (I could do this in R but I need to do it in SAS)
I think the function yrdif would be useful here.

Help is much appreciated!