Grunge, I'm not sure I believe this. Now the sole purpose of mktime is for doing arithmetic on time_t's. What a waste. Because that's just about what it amounts to if the caller has to set tm_isdst before calling mktime(). The use that most people want for mktime() is to be able to parse a string (or whatever) into the tm_hour fields, etc, and then produce a time_t .. having to second guess whether dst applied at that particular time is never going to work (and you can't look at the second char of the zone string and see if it happens to be 'D' .. even assuming that there is a zone string). This also doesn't account for time zone changes that skip hours from one dst timezone to another (when dst changes from +1 hour to +2 hours, in both cases tm_isdst will be true). kre