Hi! Don't konw much, but I worked with package "chron", function "dates": d2<-"2002-01-21" d1<-"2001-01-01" dates(d2, format="y-m-d") -dates(d1, format="y-m-d") # gives: # Time in days: # [1] 385 Actually I used something like dates(as.character(d2), format="y-m-d") cause the variable was read form a table as factor. Good luck! Karl