how to calculate recency(RFM) from a given date attribute in R
Try this

as.POSIXct(Sys.Date(), format= "%Y-%m-%d", tz="UCT") - as.POSIXct("11/25/2011", format = "%m/%d/%Y",tz="UCT")


More vectorized operation in your situation

as.POSIXct(Sys.Date(), format= "%Y-%m-%d", tz="UCT") - as.POSIXct(Last_tran, format = "%m/%d/%Y",tz="UCT")