hi the docs of time_duration say that minutes() returns 0..59 and seconds() return 0..59. this is not true, the correct answer is, minutes() returns -59..+59 and seconds() also. the handling of negative durations is not fully documented. i.e. is it true that the sign of hours(),minutes() and seconds() is always equal to each others sign? x=time_duration(anything...); y=x.invert_sign(); is the following true for all values of x: abs(x.hours()) == abs(y.hours()) abs(x.minutes()) == abs(y.minutes()) abs(x.seconds()) == abs(y.seconde()) but whatever way you document it, it should somehow be documented. to continue on my work i now make the assumption that in the following assertions are true for all values of x: if (x.is_negative()) x = x.invert_sign(); assert(x.hours()>=0); assert(0<=x.minutes()<=59); assert(0<=x.seconds()<=59); i hope this assertions are correct for all values of x !!!!! :) cya! erik