I am often taking the absolute value of a difftime object (after coercing it to numeric) in order to see how far apart in time two events are. For example, I might want to know if two events occurred within 100 days of each other using something like abs(difftime(Date1, Date2)) < 100 Below is a suggestion for an abs.difftime: abs.difftime <- function(x) { structure(abs(as.numeric(x)), class = class(x), units = attr(x, "units")) } I think these changes to difftime.Rd would document this: 1) Add \alias{abs.difftime} 2) In the first paragraph of \details change "There is a \code{\link{round}} method for objects of this class, as well as..." to "There are \code{\link{round}} and \code{\link{abs}} methods for objects of this class, as well as..." Thanks for considering this, Stephen Rochester, Minnesota, USA