I'm sure the Time class' isdst method is making a call into the standard C library, first by calling the localtime function and then looking at the tm_isdst field of the returned structure. Therefore it depends on which version of the standard C library is being called, i.e., what's installed on the machine you compiled on. Eric Interested in hands-on, on-site Ruby training? See http:// LearnRuby.com for information about a well-reviewed class.